MASSMUTUAL FUNDS

This Prospectus describes the following Funds:

Fund Name

Class I

Class R5

Service Class

Administrative
Class

Class R4

Class A

Class R3

Class Y

MassMutual Total Return Bond Fund

MSPZX

MSPSX

MSPHX

MSPLX

MSPGX

MPTRX

MSPNX

MMNNX

MassMutual Strategic Bond Fund

MSBZX

MBSSX

MBSYX

MSBLX

MSBRX

MSBAX

MSBNX

MMNMX

MassMutual Diversified Value Fund

MDDIX

MDVSX

MDVYX

MDDLX

MDDRX

MDDAX

MDVNX

MMNBX

MassMutual Fundamental Value Fund

MFUZX

MVUSX

MFUYX

MFULX

MFUFX

MFUAX

MFUNX

MMNEX

MM S&P 500® Index Fund

MMIZX

MIEZX

MMIEX

MIEYX

MIEAX

MMFFX

MMINX

MassMutual Equity Opportunities Fund

MFVZX

MFVSX

MMFYX

MMFVX

MFVFX

MFVAX

MFVNX

MMZOX

MassMutual Fundamental Growth Fund

MOTZX

MOTCX

MOTYX

MOTLX

MFGFX

MOTAX

MOTNX

MMNDX

MassMutual Blue Chip Growth Fund

MBCZX

MBCSX

MBCYX

MBCLX

MBGFX

MBCGX

MBCNX

MMZMX

MassMutual Growth Opportunities Fund

MMAZX

MGRSX

MAGYX

MAGLX

MMGFX

MMAAX

MMANX

MMNFX

MassMutual Mid Cap Value Fund

MLUZX

MLUSX

MLUYX

MLULX

MLUFX

MLUAX

MLUNX

MMNHX

MassMutual Small Cap Value Equity Fund

MMQIX

MMQSX

MMQYX

MMQLX

MMQFX

MMQAX

MMQTX

MMNKX

MassMutual Small Company Value Fund

MSVZX

MSVSX

MMVYX

MMYLX

MMVFX

MMYAX

MSVNX

MMNLX

MassMutual Mid Cap Growth Fund

MEFZX

MGRFX

MEFYX

MMELX

MEFFX

MEFAX

MEFNX

MMNGX

MassMutual Small Cap Growth Equity Fund

MSGZX

MSGSX

MSCYX

MSGLX

MSERX

MMGEX

MSGNX

MMNJX

MassMutual Overseas Fund

MOSZX

MOSSX

MOSYX

MOSLX

MOSFX

MOSAX

MOSNX

MMOJX

MassMutual Select T. Rowe Price International Equity Fund

MMIUX

The Securities and Exchange Commission has not approved or disapproved these securities or passed upon the adequacy of this Prospectus. Any statement to the contrary is a crime.

PROSPECTUS

February 1, 2023

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MassMutual Total Return Bond Fund (Class Y shares not currently available)

INVESTMENT OBJECTIVE

This Fund seeks maximum total return, consistent with preservation of capital and prudent investment management.

FEES AND EXPENSES OF THE FUND

This table describes the fees and expenses that you may pay if you buy, hold, and sell shares of the Fund. You may pay brokerage commissions and other fees to financial intermediaries which are not reflected in the tables and examples below. For Class A shares, you may qualify for sales charge discounts if you invest, or agree to invest in the future, at least $25,000 in MassMutual funds. More information about these and other discounts is available in the section titled Sales Charges by Class beginning on page 142 of the Fund’s Prospectus or from your financial professional.

Shareholder Fees (fees paid directly from your investment)

Class I

Class R5

Service
Class

Administrative
Class

Class R4

Class A

Class R3

Class Y

Maximum Sales Charge (Load) Imposed on Purchases (as a % of offering price)

None

4.25%

None

Maximum Deferred Sales Charge (Load) (as a % of the lower of the original offering price or redemption proceeds)

None

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

	Class I	Class R5	Service Class	Administrative Class	Class R4	Class A	Class R3	Class Y
Management Fees	0.30%	0.30%	0.30%	0.30%	0.30%	0.30%	0.30%	0.30%
Distribution and Service (Rule 12b-1) Fees	None	None	None	None	0.25%	0.25%	0.50%	None
Other Expenses	0.07%	0.17%	0.27%	0.37%	0.27%	0.37%	0.27%	0.17%(1)
Total Annual Fund Operating Expenses	0.37%	0.47%	0.57%	0.67%	0.82%	0.92%	1.07%	0.47%
Fee Waiver	(0.03%)	(0.03%)	(0.03%)	(0.03%)	(0.03%)	(0.03%)	(0.03%)	(0.03%)
Total Annual Fund Operating Expenses after Fee Waiver(2)	0.34%	0.44%	0.54%	0.64%	0.79%	0.89%	1.04%	0.44%

(1)

Other Expenses are based on estimated amounts for the current fiscal year of the Fund.

(2)

The expenses in the above table reflect a written agreement by MML Advisers to waive 0.03% of its management fees through January 31, 2024. This agreement can only be terminated by mutual consent of the Board of Trustees on behalf of the Fund and MML Advisers.

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. It assumes that you invest $10,000 in each share class of the Fund for the time periods indicated and then redeem

all of your shares at the end of those periods. For Class A shares, the example includes the initial sales charge. The example also assumes that your investment earns a 5% return each year and that the Fund’s operating expenses are exactly as described in the preceding table. Although your

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actual costs may be higher or lower, based on these assumptions your costs would be:

	1 Year			3 Years			5 Years			10 Years
Class I		$	35		$	116		$	205		$	465
Class R5		$	45		$	148		$	260		$	589
Service Class		$	55		$	180		$	315		$	711
Administrative Class		$	65		$	211		$	370		$	832
Class R4		$	81		$	259		$	452		$	1,011
Class A		$	512		$	703		$	910		$	1,506
Class R3		$	106		$	337		$	587		$	1,303
Class Y		$	45		$	148		$	260		$	589

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 442% of the average value of its portfolio.

INVESTMENTS, RISKS, AND PERFORMANCE

Principal Investment Strategies

Under normal circumstances, the Fund invests at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in a diversified portfolio of investment grade fixed income securities (rated Baa3 or higher by Moody’s, BBB- or higher by Standard & Poor’s, BBB- or higher by Fitch, or A-2 by S&P, P-2 by Moody’s, or F-2 by Fitch for short-term debt obligations, or, if unrated, determined by the Fund’s subadviser, Metropolitan West Asset Management, LLC (“MetWest”), to be of comparable quality). These typically include bonds, notes, collateralized bond obligations, collateralized debt obligations, mortgage-related and asset-backed securities, municipal securities, private placements, and securities subject to legal restrictions on resale pursuant to Rule 144A. These investments may have interest rates that are fixed, variable, or floating. The Fund invests in securities of varying maturities issued by domestic and foreign corporations and governments (and their agencies and instrumentalities). MetWest focuses the Fund’s portfolio holdings in areas of the bond market (based on quality, sector, coupon, or maturity) that the subadviser believes to be relatively undervalued.

The Fund may invest up to 20% of its net assets in below investment grade debt securities (“junk” or “high yield” bonds), including securities in default and bank loans. In the event that a security is downgraded after its purchase by the Fund, the Fund may continue to hold the security if MetWest considers doing so would be consistent with the Fund’s investment objective.

The Fund may invest up to 25% of its total assets in foreign securities that are denominated in U.S. dollars. The Fund may also invest up to 15% of its total assets in foreign securities that are not denominated in U.S. dollars and up to 10% of its total assets in emerging market foreign securities.

The Fund may but will not necessarily engage in foreign currency forward transactions to take long or short positions in foreign currencies in order to seek to enhance the Fund’s investment return or to seek to hedge or to attempt to protect against adverse changes in currency exchange rates. In pursuing its investment objective, the Fund may (but is not obligated to) use a wide variety of exchange-traded and over-the-counter derivatives, including options, futures contracts, and swap contracts for hedging or investment purposes as a substitute for investing directly in securities or to adjust various portfolio characteristics, including the duration (interest rate volatility) of the Fund’s portfolio. Use of derivatives by the Fund may create investment leverage.

The Fund may purchase and sell securities on a when-issued, delayed delivery, or forward commitment basis. The Fund may normally short sell up to 25% of the value of its total assets for hedging or investment purposes.

The Fund may also invest in money market securities, including commercial paper. The Fund may enter into repurchase agreement transactions. The Fund may at times have significant exposure to one or more industries or sectors. The Fund may hold a portion of its assets in cash or cash equivalents. The Fund may enter into dollar roll or reverse repurchase agreement transactions.

MetWest intends for the Fund’s portfolio duration to be between two to eight years. The dollar-weighted average maturity of the Fund’s portfolio is expected to range from two to fifteen years. Duration measures the price sensitivity of a bond to changes in interest rates. Duration is the dollar weighted average time to maturity of a bond utilizing the present value of all future cash flows.

MetWest employs a value-oriented fixed income management philosophy with a goal of consistently outperforming the portfolio benchmark while

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maintaining volatility similar to the benchmark. The investment process is predicated on a long-term economic outlook, which is determined by the investment team on a quarterly basis and is reviewed constantly. Investments are characterized by diversification among the sectors of the fixed income marketplace. The investment management team seeks to achieve the desired outperformance through the measured and disciplined application of five fixed income management strategies which include duration management, yield curve positioning, sector allocation, security selection, and opportunistic execution.

The first three strategies are top-down in orientation and start with a decision of where within the plus-or-minus one year range around the benchmark the duration should be established. Then comes a determination of how the overall average duration is to be effected – with a concentration of intermediate maturity issues or a combination of long- and short-term issues. The relative value decision regarding where to overweight/underweight sectors, including governments, agencies, corporates, mortgages, or asset-backed securities, is dependent on the current market environment. Bottom-up security selection involves the day-to-day fundamental analysis of available bond market opportunities, while execution is characterized by the aggressive and informed negotiation of the prices at which transactions take place.

The Fund expects that it will engage in active and frequent trading and so will typically have a relatively high portfolio turnover rate.

Principal Risks

The following are the Principal Risks of the Fund. The value of your investment in the Fund could go down as well as up. You can lose money by investing in the Fund. Certain risks relating to instruments and strategies used in the management of the Fund are placed first. The significance of any specific risk to an investment in the Fund will vary over time, depending on the composition of the Fund’s portfolio, market conditions, and other factors. You should read all of the risk information presented below carefully, because any one or more of these risks may result in losses to the Fund.

of the issuer, borrower, counterparty, or underlying collateral assets, or changes in market, economic, industry, political, regulatory, public health, and other conditions affecting a particular type of security or issuer or fixed income securities generally. Certain events, such as market or economic developments, regulatory or government actions, natural disasters, pandemics, terrorist attacks, war, and other geopolitical events can have a dramatic adverse effect on the debt market and the overall liquidity of the market for fixed income securities. During those periods, the Fund may experience high levels of shareholder redemptions, and may have to sell securities at times when the Fund would otherwise not do so, and potentially at unfavorable prices. Certain securities may be difficult to value during such periods. Fixed income securities are subject to interest rate risk (the risk that the value of a fixed income security will fall when interest rates rise), extension risk (the risk that the average life of a security will be extended through a slowing of principal payments), prepayment risk (the risk that a security will be prepaid and the Fund will be required to reinvest at a less favorable rate), duration risk (the risk that longer-term securities may be more sensitive to interest rate changes), inflation risk (the risk that as inflation increases, the present value of the Fund’s fixed income investment typically will decline), and credit risk.

Bank Loans Risk Many of the risks associated with bank loans are similar to the risks of investing in below investment grade debt securities. Changes in the financial condition of the borrower or economic conditions or other circumstances may reduce the capacity of the borrower to make principal and interest payments on such instruments and may lead to defaults. Senior secured bank loans are typically supported by collateral; however the value of the collateral may be insufficient to cover the amount owed to the Fund, or the Fund may be prevented or delayed from realizing on the collateral. Some loans may be unsecured; unsecured loans generally present a greater risk of loss to the Fund if the issuer defaults. If the Fund relies on a third party to administer a loan, the Fund is subject to the risk that the third party will fail to perform its obligations. In addition, if the Fund holds only a participation interest in a loan made by a third party, the Fund’s receipt of payments on the loan will depend on the third party’s willingness and ability to make those payments to the Fund. The settlement time for certain loans is longer than the settlement time for many other types of

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investments, and the Fund may not receive the payment for a loan sold by it until well after the sale; that cash would be unavailable for payment of redemption proceeds or for reinvestment. Interests in some bank loans may not be readily marketable and may be subject to restrictions on resale. In some cases, negotiations involved in disposing of indebtedness may require weeks to complete. Consequently, some indebtedness may be difficult or impossible to dispose of readily at what the Fund believes to be a fair price. Some loans may not be considered “securities” for certain purposes under the federal securities laws, and purchasers, such as the Fund, therefore may not be entitled to rely on the anti-fraud protections of the federal securities laws.

Below Investment Grade Debt Securities Risk Below investment grade debt securities, commonly known as “junk” or “high yield” bonds, have speculative characteristics and involve greater volatility of price and yield, greater risk of loss of principal and interest, and generally reflect a greater possibility of an adverse change in financial condition that could affect an issuer’s ability to honor its obligations.

Credit Risk Credit risk is the risk that an issuer, guarantor, or liquidity provider of a fixed income security held by the Fund may be unable or unwilling, or may be perceived (whether by market participants, ratings agencies, pricing services or otherwise) as unable or unwilling, to make timely principal and/or interest payments, or to otherwise honor its obligations. The Fund may also be exposed to the credit risk of its counterparty to repurchase agreements, reverse repurchase agreements, swap transactions, and other derivatives transactions, and to the counterparty’s ability or willingness to perform in accordance with the terms of the transaction. The value of such transactions to the Fund will depend on the willingness and ability of the counterparty to perform its obligations, including among other things the obligation to return collateral or margin to the Fund. If a counterparty becomes bankrupt or otherwise fails to perform its obligations under a derivative contract due to financial difficulties, the Fund may experience significant delays in obtaining any recovery under the derivative contract in a bankruptcy or other reorganization proceeding. The Fund may obtain only a limited recovery or may obtain no recovery in such circumstances.

Derivatives Risk Derivatives can be highly volatile and involve risks different from, and potentially

greater than, direct investments, including risks of imperfect correlation between the value of derivatives and underlying assets, counterparty default, potential losses that partially or completely offset gains, and illiquidity. Derivatives can create investment leverage. Losses from derivatives can be substantially greater than the derivatives’ original cost and can sometimes be unlimited. If the value of a derivative does not correlate well with the particular market or asset class the derivative is designed to provide exposure to, the derivative may not have the effect or benefit anticipated. Derivatives can also reduce the opportunity for gains or result in losses by offsetting positive returns in other investments. Many derivatives are traded in the over-the-counter market and not on exchanges.

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withholding and other taxes. There may be less information publicly available about a non-U.S. company than about a U.S. company, and many non-U.S. companies are not subject to accounting, auditing, and financial reporting standards, regulatory framework and practices comparable to those in the U.S. The securities of some non-U.S. companies, especially those in emerging markets, are less liquid and at times more volatile than securities of comparable U.S. companies. Emerging markets securities are subject to greater risks than securities issued in developed foreign markets, including less liquidity, less stringent investor protection and disclosure standards, less reliable settlement practices, greater price volatility, higher relative rates of inflation, greater political, economic, and social instability, greater custody and operational risks, greater risk of new or inconsistent government treatment of or restrictions on issuers and instruments, and greater volatility in currency exchange rates, and are more susceptible to environmental problems. Many emerging market countries are highly reliant on international trade and exports, including the export of commodities. Their economies may be significantly impacted by fluctuations in commodity prices and the global demand for certain commodities. In addition, pandemics and outbreaks of contagious diseases may exacerbate pre-existing problems in emerging market countries with less established health care systems. Frontier markets, a subset of emerging markets, generally have smaller economies and less mature capital markets than emerging markets. As a result, the risks of investing in emerging market countries are magnified in frontier market countries. Frontier markets are more susceptible to having abrupt changes in currency values, less mature markets and settlement practices, and lower trading volumes that could lead to greater price volatility and illiquidity. Non-U.S. transaction costs, such as brokerage commissions and custody costs, may be higher than in the United States. In addition, foreign markets can react differently to market, economic, industry, political, regulatory, geopolitical, public health, and other conditions than the U.S. market.

of principal and interest generally depends on the cash flows generated by the underlying assets and the terms of the security. The types of mortgages (for example, residential or commercial mortgages) underlying securities held by the Fund may differ and be affected differently by market factors. Investments that receive only the interest portion or the principal portion of payments on the underlying assets may be highly volatile. Litigation with respect to the representations and warranties given in connection with the issuance of mortgage-backed securities can be an important consideration in investing in such securities, and the outcome of any such litigation could significantly impact the value of the Fund’s mortgage-backed investments.

Short Sales Risk If the Fund sells a security short, it will make money if the security’s price goes down (in an amount greater than any transaction costs) and will lose money if the security’s price goes up. There is no limit on the amount of money the Fund may lose on a short sale. The Fund may not be able to close out a short sale when it might wish to do so, or may only do so at an unfavorable price. Short sales can involve leverage. If the Fund invests the proceeds from short positions in other securities the Fund could lose money both on the short positions and on the securities in which it has invested the short proceeds.

Cash Position Risk If the Fund holds a significant portion of its assets in cash or cash equivalents, its investment returns may be adversely affected and the Fund may not achieve its investment objective.

Defaulted and Distressed Securities Risk Because the issuer of such securities is in default and is likely to be in distressed financial condition, repayment of defaulted securities and obligations of distressed issuers (including insolvent issuers or issuers in payment or covenant default, in workout or restructuring, or in bankruptcy or insolvency proceedings) is uncertain. To the extent the Fund is invested in distressed securities, its ability to achieve current income for its shareholders may be diminished.

Dollar Roll and Reverse Repurchase Agreement Transaction Risk These transactions generally create leverage and subject the Fund to the credit risk of the counterparty.

Frequent Trading/Portfolio Turnover Risk Portfolio turnover generally involves some expense to the Fund and may result in the realization of taxable

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capital gains (including short-term gains). The trading costs and tax effects associated with portfolio turnover may adversely affect the Fund’s performance.

Hedging Risk The Fund’s attempts at hedging and taking long and short positions in currencies may not be successful and could cause the Fund to lose money or fail to get the benefit of a gain on a hedged position. If expected changes to securities prices, interest rates, currency values, and exchange rates, or the creditworthiness of an issuer are not accurately predicted, the Fund could be in a worse position than if it had not entered into such transactions.

Inflation Risk The value of assets or income from the Fund’s investments will be less in the future as inflation decreases the value of money. As inflation increases, the value of the Fund’s assets can decline as can the value of the Fund’s distributions. Inflation rates may change frequently and drastically as a result of various factors, including unexpected shifts in the domestic or global economy (or expectations that such policies will change), and the Fund’s investments may not keep pace with inflation, which may result in losses to the Fund’s investors.

Leveraging Risk Instruments and transactions, including derivatives, dollar roll, and reverse repurchase agreement transactions, that create leverage may cause the value of an investment in the Fund to be more volatile, could result in larger losses than if they were not used, and tend to compound the effects of other risks.

LIBOR Risk Certain instruments in which the Fund may invest rely in some fashion upon the London-Interbank Offered Rate (“LIBOR”). On July 27, 2017, the head of the United Kingdom’s Financial Conduct Authority announced a desire to phase out the use of LIBOR by the end of 2021. The administrator of LIBOR ceased publication of most LIBOR settings on a representative basis at the end of 2021 and is expected to cease publication of remaining U.S. dollar LIBOR settings on a representative basis after June 30, 2023. In addition, global regulators have announced that, with limited exceptions, no new LIBOR-based contracts should be entered into after 2021. Actions by regulators have resulted in the establishment of alternative reference rates to LIBOR in most major currencies. Market participants are focused on the transition mechanisms by which the reference rate in existing contracts or instruments may be amended, whether

through market wide protocols, fallback contractual provisions, bespoke negotiations or amendments, or otherwise. Markets are developing in response to these new rates, and questions around liquidity in these rates and how to appropriately adjust these rates to eliminate any economic value transfer at the time of transition remain a significant concern for the Fund. Neither the effect of the transition process nor its ultimate success can yet be known. The transition process may involve, among other things, increased volatility or illiquidity in markets for instruments that rely on LIBOR. In addition, uncertainty and volatility arising from the transition may result in a reduction in the value of certain LIBOR-based instruments held by the Fund or reduce the effectiveness of related transactions such as hedges. Any such effects of the transition away from LIBOR, as well as other unforeseen effects, could result in losses to the Fund.

Liquidity Risk Certain securities may be difficult (or impossible) to sell or certain positions may be difficult to close out at a desirable time and price, and the Fund may be required to hold an illiquid investment that is declining in value, or it may be required to sell certain illiquid investments at a price or time that is not advantageous in order to meet redemptions or other cash needs. Some securities may be subject to restrictions on resale. There can be no assurance that there will be a liquid market for instruments held by the Fund at any time. The Fund may not receive the proceeds from the sale of certain investments for an extended period.

Management Risk The Fund relies on the manager’s investment analysis and its selection of investments to achieve its investment objective. There can be no assurance that the Fund will achieve the intended results and the Fund may incur significant losses.

Market Risk The value of the Fund’s portfolio securities may decline, at times sharply and unpredictably, as a result of unfavorable market-induced changes affecting particular industries, sectors, or issuers. Stock and bond markets can decline significantly in response to issuer, market, economic, industry, political, regulatory, geopolitical, public health, and other conditions, as well as investor perceptions of these conditions. The Fund is subject to risks affecting issuers, such as management performance, financial leverage, industry problems, and reduced demand for goods or services.

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Municipal Securities Risk The risk of investing in municipal securities, including that the issuers of municipal securities may be unable to pay their obligations as they come due. The values of municipal securities may fluctuate as a result of changes in the cash flows generated by the revenue source or changes in the priority of the municipal obligation to receive the cash flows generated by the revenue source. Changes in federal tax laws or the activity of an issuer may adversely affect the tax-exempt status of municipal securities, may cause interest received and distributed to shareholders by the Fund to be taxable, and may result in a significant decline in the values of such municipal securities.

Reinvestment Risk Income from the Fund’s portfolio will decline if and when the Fund invests the proceeds from matured, traded, or called debt obligations at market interest rates that are below the portfolio’s current earnings rate. A decline in income could affect the Fund’s overall return.

Repurchase Agreement Risk These transactions must be fully collateralized, but involve credit risk to a Fund if the other party should default on its obligation and the Fund is delayed or prevented from recovering the collateral.

Restricted Securities Risk The Fund may hold securities that are restricted as to resale under the U.S. federal securities laws, such as securities in certain privately held companies. Such securities may be highly illiquid and their values may experience significant volatility. Restricted securities may be difficult to value.

Sector Risk The Fund may allocate more of its assets to particular industries or to particular economic, market, or industry sectors than to others. This could increase the volatility of the Fund’s portfolio, and the Fund’s performance may be more susceptible to developments affecting issuers in those industries or sectors than if the Fund invested more broadly.

Any restructuring of a sovereign debt obligation held by the Fund will likely have a significant adverse effect on the value of the obligation. In the event of default of sovereign debt, the Fund may be unable to pursue legal action against the sovereign issuer or to realize on collateral securing the debt.

U.S. Government Securities Risk Obligations of certain U.S. Government agencies and instrumentalities are not backed by the full faith and credit of the U.S. Government, and there can be no assurance that the U.S. Government would provide financial support to such agencies and instrumentalities.

Valuation Risk The Fund is subject to the risk of mispricing or improper valuation of its investments, in particular to the extent that its securities are fair valued.

When-Issued, Delayed Delivery, TBA, and Forward Commitment Transaction Risk These transactions may create leverage and involve a risk of loss if the value of the securities declines prior to settlement.

Performance Information

The following bar chart and table provide some indication of the risks of investing in the Fund. The bar chart shows changes in the Fund’s performance from year to year for Class I shares. The table shows how the Fund’s average annual returns for 1, 5, and 10 years compare with those of a broad measure of market performance. The Fund’s name and investment strategy changed on October 27, 2014. The performance results shown below would not necessarily have been achieved had the Fund’s current investment strategy been in effect for the entire period for which performance results are presented. Performance for Class A shares of the Fund for periods prior to its inception date (04/01/14) and performance for Class Y shares of the Fund for periods prior to its inception date (02/01/23) is based on the performance of Class R5 shares, adjusted for Class A shares to reflect Class A expenses. Performance for Class A shares of the Fund reflects any applicable sales charge. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. More up-to-date performance information is available at https://www.massmutual.com/funds or by calling 1-888-309-3539.

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Annual Performance

Class I Shares

[MISSING IMAGE: a9c2j7aghrgi9mbm4dsu6f1ff8eo.jpg]

Highest
Quarter:

2Q ’20,

4.00%

Lowest
Quarter:

1Q ’22,

–6.19%

After-tax returns are calculated using the historical highest individual U.S. federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns are not relevant to investors who hold Fund shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement accounts. After-tax returns are shown for Class I only. After-tax returns for other classes will vary.

Average Annual Total Returns

(for the periods ended December 31, 2022)

		One Year			Five Years			Ten Years
Class I	Return Before Taxes		-14.24	%		0.24	%		1.08	%
	Return After Taxes on Distributions		-15.15	%		-1.08	%		-0.29	%
	Return After Taxes on Distributions and Sales of Fund Shares		-8.42	%		-0.32	%		0.27	%
Class R5	Return Before Taxes		-14.34	%		0.15	%		0.97	%
Service Class	Return Before Taxes		-14.36	%		0.06	%		0.87	%
Administrative Class	Return Before Taxes		-14.46	%		-0.05	%		0.78	%
Class R4	Return Before Taxes		-14.65	%		-0.21	%		0.62	%
Class A	Return Before Taxes		-18.37	%		-1.16	%		0.10	%
Class R3	Return Before Taxes		-14.84	%		-0.46	%		0.37	%
Class Y	Return Before Taxes		-14.34	%		0.15	%		0.97	%
Bloomberg U.S. Aggregate Bond Index (reflects no deduction for fees, expenses, or taxes)			-13.01	%		0.02	%		1.06	%

MANAGEMENT

Investment Adviser: MML Investment Advisers, LLC (“MML Advisers”)

Subadviser(s): Metropolitan West Asset Management, LLC (“MetWest”)

Portfolio Manager(s):

Stephen M. Kane, CFA is a Group Managing Director, and a Generalist Portfolio Manager and Co-Chief Investment Officer for the U.S. Fixed Income Group at MetWest. He has managed the Fund since October 2014.

Laird R. Landmann is the President and a Generalist Portfolio Manager at MetWest. He has managed the Fund since October 2014.

Bryan T. Whalen, CFA is a Group Managing Director, and a Generalist Portfolio Manager and Co-Chief Investment Officer for the U.S. Fixed Income Group at MetWest. He has managed the Fund since October 2014.

PURCHASE AND SALE OF FUND SHARES

Shares of the Fund are generally available through distribution channels, such as broker-dealers or financial institutions, and to retirement plans, other institutional investors, and individual retirement accounts. Fund shares are redeemable on any business day by written request, telephone, or internet (available to certain customers).

Purchase Minimums*

Class Y

Initial Investment

$100,000

Subsequent Investment

$250

The Fund reserves the right to change or waive the investment minimums. For retirement plans, the investment minimum is $250 for each of the initial investment and subsequent investments.

TAX INFORMATION

The Fund intends to make distributions that may be taxed as ordinary income, qualified dividend income, or capital gains, unless you are an investor eligible for preferential tax treatment.

PAYMENTS TO BROKER-DEALERS AND OTHER FINANCIAL INTERMEDIARIES

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MassMutual Strategic Bond Fund

INVESTMENT OBJECTIVE

This Fund seeks a superior total rate of return by investing in fixed income instruments.

FEES AND EXPENSES OF THE FUND

Shareholder Fees (fees paid directly from your investment)

Class I

Class R5

Service
Class

Administrative
Class

Class R4

Class A

Class R3

Class Y

Maximum Sales Charge (Load) Imposed on Purchases (as a % of offering price)

None

4.25%

None

Maximum Deferred Sales Charge (Load) (as a % of the lower of the original offering price or redemption proceeds)

None

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

	Class I	Class R5	Service Class	Administrative Class	Class R4	Class A	Class R3	Class Y
Management Fees	0.39%	0.39%	0.39%	0.39%	0.39%	0.39%	0.39%	0.39%
Distribution and Service (Rule 12b-1) Fees	None	None	None	None	0.25%	0.25%	0.50%	None
Other Expenses	0.12%	0.22%	0.32%	0.42%	0.32%	0.42%	0.32%	0.22%(1)
Total Annual Fund Operating Expenses	0.51%	0.61%	0.71%	0.81%	0.96%	1.06%	1.21%	0.61%
Fee Waiver	(0.05%)	(0.05%)	(0.05%)	(0.05%)	(0.05%)	(0.05%)	(0.05%)	(0.05%)
Total Annual Fund Operating Expenses after Fee Waiver(2)	0.46%	0.56%	0.66%	0.76%	0.91%	1.01%	1.16%	0.56%

(1)

Other Expenses are based on estimated amounts for the current fiscal year of the Fund.

(2)

The expenses in the above table reflect a written agreement by MML Advisers to waive 0.05% of its management fees through January 31, 2024. This agreement can only be terminated by mutual consent of the Board of Trustees on behalf of the Fund and MML Advisers.

Example

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actual costs may be higher or lower, based on these assumptions your costs would be:

	1 Year			3 Years			5 Years			10 Years
Class I		$	47		$	159		$	280		$	636
Class R5		$	57		$	190		$	335		$	757
Service Class		$	67		$	222		$	390		$	878
Administrative Class		$	78		$	254		$	445		$	997
Class R4		$	93		$	301		$	526		$	1,173
Class A		$	524		$	743		$	980		$	1,660
Class R3		$	118		$	379		$	660		$	1,462
Class Y		$	57		$	190		$	335		$	757

Portfolio Turnover

INVESTMENTS, RISKS, AND PERFORMANCE

Principal Investment Strategies

Under normal circumstances, the Fund invests at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in U.S. dollar-denominated fixed income securities and other debt instruments of domestic and foreign entities, including corporate bonds, securities issued or guaranteed as to principal or interest by the U.S. Government or its agencies or instrumentalities, mortgage-backed securities, and money market instruments. The Fund may invest up to 20% of its total assets in non-U.S. dollar-denominated securities of these entities. The Fund may invest in emerging markets. The Fund may but will not necessarily engage in foreign currency transactions, including forward contracts, options on currency, futures contracts, and swap contracts, to attempt to seek to hedge or to protect against adverse changes in currency exchange rates. In pursuing its investment objective, the Fund may (but is not obligated to) use a wide variety of additional exchange-traded and over-the-counter derivatives, including futures contracts (for hedging purposes or to adjust various portfolio characteristics, including the duration (interest rate volatility) of the Fund’s portfolio); interest rate swaps (for hedging purposes or to adjust various

portfolio characteristics, including the duration (interest rate volatility) of the Fund’s portfolio); credit default swaps (for hedging purposes, to earn additional income, or as a substitute for direct investments); and hybrid instruments (as a substitute for direct investments). The Fund may also purchase and sell exchange-traded and over-the-counter options for hedging purposes, to adjust various portfolio characteristics, including the duration (interest rate volatility) of the Fund’s portfolio, or as a substitute for direct investments. Use of derivatives by the Fund may create investment leverage. The Fund may purchase and sell securities on a when-issued, delayed delivery, or forward commitment basis. The Fund may also invest in money market securities, including commercial paper. The Fund may at times have significant exposure to one or more industries or sectors. The Fund may hold a portion of its assets in cash or cash equivalents. The Fund is managed by three subadvisers, Western Asset Management Company, LLC (“Western Asset”), Western Asset Management Company Limited (“Western Asset Limited”), and Brandywine Global Investment Management, LLC (“Brandywine Global”), each being responsible for a portion of the portfolio, although they may manage different amounts of the Fund’s assets.

The Fund invests primarily in investment grade securities (rated Baa or higher by Moody’s or BBB or higher by Standard & Poor’s, or, if unrated, determined by the subadviser to be of comparable quality), but may invest up to 25% of the portfolio in below investment grade debt securities (“junk” or “high yield” bonds), including securities in default. In the event that a security is downgraded after its purchase by the Fund, the Fund may continue to hold the security if Western Asset or Brandywine Global consider that doing so would be consistent with the Fund’s investment objective. Certain fixed income securities in which the Fund may invest pay interest at variable or floating rates. Variable rate securities tend to reset at specified intervals, while floating rate securities may reset upon a change in a specified index rate. In most cases, these reset provisions reduce the impact of changes in market interest rates on the value of the security. However, some securities do not track the underlying index directly, but reset based on formulas that may produce a leveraging effect; others may also provide for interest payments that vary inversely with market rates. The market prices of these securities may fluctuate significantly when interest rates change. The Fund may also acquire, and subsequently hold, warrants

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and other equity interests. The Fund’s effective duration is normally expected to be between three and nine years. If the Fund’s effective duration falls outside of this range, the Fund will take action to bring it within its expected range within a reasonable period of time. Duration measures the price sensitivity of a bond to changes in interest rates. Duration is the dollar weighted average time to maturity of a bond utilizing the present value of all future cash flows. Effective duration measures the price sensitivity of a bond with embedded options to changes in interest rates. It provides a more accurate measure of price volatility when, due to the embedded options, the cash flow characteristics of the bond change as interest rates shift.

Western Asset invests in the fixed income markets seeking to exceed returns of the Fund’s benchmark while approximating benchmark risk. Western Asset focuses on sector allocation, issue selection, duration weighting, and term structure when buying and selling securities for the Fund. Western Asset emphasizes diversification, the use of multiple strategies and identification of long-term trends. The three key factors that determine Western Asset’s allocation decisions for the Fund are: Western Asset’s broad economic outlook, its review of historical yield spreads for debt instruments versus Treasuries, and its evaluation of changes in credit quality and the corresponding impact on prices. Western Asset will determine the portion of the Fund’s assets it is responsible for to be allocated to non-U.S. dollar denominated securities from time to time. Western Asset Limited, an affiliate of Western Asset, has subadvisory responsibility for Western Asset’s non-U.S. dollar denominated investments. Western Asset Limited will select such investments based on its consideration of factors such as relative interest rates, inflation rates, exchange rates, monetary and fiscal policies, and trade and current account balances.

Brandywine Global follows a value-driven, active, strategic approach to buying and selling securities for the Fund that considers duration, yield curve exposure, credit exposure, and sector weightings that are based upon the broad investment themes of its global macroeconomic research platform as they apply to U.S. markets. As part of its investment process, Brandywine Global develops an outlook for macroeconomic variables such as inflation, growth, and unemployment in the U.S., as well as in other countries that may impact U.S. fixed income sectors. Brandywine Global then

develops a viewpoint on the business cycle and positions the strategy’s duration, sector weighting and credit exposures accordingly.

The Fund expects that it will engage in active and frequent trading and so will typically have a relatively high portfolio turnover rate.

Principal Risks

Fixed Income Securities Risk The values of fixed income securities typically will decline during periods of rising interest rates, and can also decline in response to changes in the financial condition of the issuer, borrower, counterparty, or underlying collateral assets, or changes in market, economic, industry, political, regulatory, public health, and other conditions affecting a particular type of security or issuer or fixed income securities generally. Certain events, such as market or economic developments, regulatory or government actions, natural disasters, pandemics, terrorist attacks, war, and other geopolitical events can have a dramatic adverse effect on the debt market and the overall liquidity of the market for fixed income securities. During those periods, the Fund may experience high levels of shareholder redemptions, and may have to sell securities at times when the Fund would otherwise not do so, and potentially at unfavorable prices. Certain securities may be difficult to value during such periods. Fixed income securities are subject to interest rate risk (the risk that the value of a fixed income security will fall when interest rates rise), extension risk (the risk that the average life of a security will be extended through a slowing of principal payments), prepayment risk (the risk that a security will be prepaid and the Fund will be required to reinvest at a less favorable rate), duration risk (the risk that longer-term securities may be more sensitive to interest rate changes), inflation risk (the risk that as inflation increases, the present value of the Fund’s fixed income investment typically will decline), and credit risk.

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Derivatives Risk Derivatives can be highly volatile and involve risks different from, and potentially greater than, direct investments, including risks of imperfect correlation between the value of derivatives and underlying assets, counterparty default, potential losses that partially or completely offset gains, and illiquidity. Derivatives can create investment leverage. Losses from derivatives can be substantially greater than the derivatives’ original cost and can sometimes be unlimited. If the value of a derivative does not correlate well with the particular market or asset class the derivative is designed to provide exposure to, the derivative may not have the effect or benefit anticipated. Derivatives can also reduce the opportunity for gains or result in losses by offsetting positive returns in other investments. Many derivatives are traded in the over-the-counter market and not on exchanges.

Foreign Investment Risk; Emerging Markets Risk; Currency Risk Investments in securities of foreign issuers, securities of companies with significant foreign exposure, and foreign currencies can involve additional risks relating to market, industry, political, regulatory, public health, and other conditions. Political, social, diplomatic, and economic developments, U.S. and foreign government action, or threat thereof, such as the imposition of currency or capital blockages, controls, or tariffs, economic and trade sanctions or embargoes, security trading suspensions, entering or exiting trade or other intergovernmental agreements, or the expropriation or nationalization of assets in a particular country, can cause dramatic declines in certain or all securities with exposure to that country and other countries. In the event of nationalization, expropriation, confiscation, or other government action, intervention, or restriction, the Fund could lose its entire investment in a particular foreign issuer or country. There may be quotas or other limits on the ability of the Fund (or clients of the Fund’s investment adviser or subadviser) to invest or maintain investments in securities of issuers in certain countries. Enforcing legal rights can be more difficult, costly, and limited in certain foreign countries and with respect to certain types of investments, and can be particularly difficult against foreign governments. Because non-U.S. securities are normally denominated and traded in currencies other than the U.S. dollar, the value of the Fund’s assets may be affected favorably or unfavorably by changes in currency exchange rates, exchange control regulations, and restrictions or prohibitions on the repatriation of non-U.S. currencies. Income and gains with respect to investments in certain countries may be subject to withholding and other taxes. There may be less information publicly available about a non-U.S. company than about a U.S. company, and many non-U.S. companies are not subject to accounting, auditing, and financial reporting standards, regulatory framework and practices comparable to those in the U.S. The securities of some non-U.S. companies, especially those in emerging markets, are less liquid and at times more volatile than securities of comparable U.S. companies. Emerging markets securities are subject to greater risks than securities issued in developed foreign markets, including less liquidity, less stringent investor protection and disclosure standards, less reliable settlement practices, greater price volatility, higher relative rates of inflation, greater political, economic, and social instability, greater custody

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and operational risks, greater risk of new or inconsistent government treatment of or restrictions on issuers and instruments, and greater volatility in currency exchange rates, and are more susceptible to environmental problems. Many emerging market countries are highly reliant on international trade and exports, including the export of commodities. Their economies may be significantly impacted by fluctuations in commodity prices and the global demand for certain commodities. In addition, pandemics and outbreaks of contagious diseases may exacerbate pre-existing problems in emerging market countries with less established health care systems. Frontier markets, a subset of emerging markets, generally have smaller economies and less mature capital markets than emerging markets. As a result, the risks of investing in emerging market countries are magnified in frontier market countries. Frontier markets are more susceptible to having abrupt changes in currency values, less mature markets and settlement practices, and lower trading volumes that could lead to greater price volatility and illiquidity. Non-U.S. transaction costs, such as brokerage commissions and custody costs, may be higher than in the United States. In addition, foreign markets can react differently to market, economic, industry, political, regulatory, geopolitical, public health, and other conditions than the U.S. market.

Mortgage- and Asset-Backed Securities Risk Investments in mortgage- and asset-backed securities subject the Fund to credit risk, interest rate risk, extension risk, and prepayment risk, among other risks. Mortgage-backed and asset-backed securities not issued by a government agency generally involve greater credit risk than securities issued by government agencies. Payment of principal and interest generally depends on the cash flows generated by the underlying assets and the terms of the security. The types of mortgages (for example, residential or commercial mortgages) underlying securities held by the Fund may differ and be affected differently by market factors. Investments that receive only the interest portion or the principal portion of payments on the underlying assets may be highly volatile. Litigation with respect to the representations and warranties given in connection with the issuance of mortgage-backed securities can be an important consideration in investing in such securities, and the outcome of any such litigation could significantly impact the value of the Fund’s mortgage-backed investments.

Cash Position Risk If the Fund holds a significant portion of its assets in cash or cash equivalents,

its investment returns may be adversely affected and the Fund may not achieve its investment objective.

Frequent Trading/Portfolio Turnover Risk Portfolio turnover generally involves some expense to the Fund and may result in the realization of taxable capital gains (including short-term gains). The trading costs and tax effects associated with portfolio turnover may adversely affect the Fund’s performance.

Leveraging Risk Instruments and transactions, including derivatives transactions, that create leverage may cause the value of an investment in the Fund to be more volatile, could result in larger losses than if they were not used, and tend to compound the effects of other risks.

LIBOR Risk Certain instruments in which the Fund may invest rely in some fashion upon the

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London-Interbank Offered Rate (“LIBOR”). On July 27, 2017, the head of the United Kingdom’s Financial Conduct Authority announced a desire to phase out the use of LIBOR by the end of 2021. The administrator of LIBOR ceased publication of most LIBOR settings on a representative basis at the end of 2021 and is expected to cease publication of remaining U.S. dollar LIBOR settings on a representative basis after June 30, 2023. In addition, global regulators have announced that, with limited exceptions, no new LIBOR-based contracts should be entered into after 2021. Actions by regulators have resulted in the establishment of alternative reference rates to LIBOR in most major currencies. Market participants are focused on the transition mechanisms by which the reference rate in existing contracts or instruments may be amended, whether through market wide protocols, fallback contractual provisions, bespoke negotiations or amendments, or otherwise. Markets are developing in response to these new rates, and questions around liquidity in these rates and how to appropriately adjust these rates to eliminate any economic value transfer at the time of transition remain a significant concern for the Fund. Neither the effect of the transition process nor its ultimate success can yet be known. The transition process may involve, among other things, increased volatility or illiquidity in markets for instruments that rely on LIBOR. In addition, uncertainty and volatility arising from the transition may result in a reduction in the value of certain LIBOR-based instruments held by the Fund or reduce the effectiveness of related transactions such as hedges. Any such effects of the transition away from LIBOR, as well as other unforeseen effects, could result in losses to the Fund.

Management Risk The Fund relies on the manager’s investment analysis and its selection of

investments to achieve its investment objective. There can be no assurance that the Fund will achieve the intended results and the Fund may incur significant losses.

Sovereign Debt Obligations Risk Investments in debt securities issued by governments or by government agencies and instrumentalities involve the risk that the governmental entities responsible for repayment may be unable or unwilling to pay interest and repay principal when due. Many sovereign debt obligations may be rated below investment grade (“junk” or “high yield” bonds). Any restructuring of a sovereign debt obligation held by the Fund will likely have a significant adverse effect on the value of the obligation. In the event of default of sovereign debt, the Fund may be unable to pursue legal action against the sovereign issuer or to realize on collateral securing the debt.

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Valuation Risk The Fund is subject to the risk of mispricing or improper valuation of its investments, in particular to the extent that its securities are fair valued.

Performance Information

The following bar chart and table provide some indication of the risks of investing in the Fund. The bar chart shows changes in the Fund’s performance from year to year for Class R5 shares. The table shows how the Fund’s average annual returns for 1, 5, and 10 years compare with those of a broad measure of market performance. Performance for Class I and Class R4 shares of the Fund for periods prior to their inception date (04/01/14) and performance for Class Y shares of the Fund for periods prior to its inception date (02/01/23) is based on the performance of Class R5 shares, adjusted for Class R4 shares to reflect Class R4 expenses. Performance for Class A shares of the Fund reflects any applicable sales charge. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. More up-to-date performance information is available at https://www.massmutual.com/funds or by calling 1-888-309-3539.

Annual Performance

Class R5 Shares

[MISSING IMAGE: mvntlt7tbtjah58dfccb4b2g29v3.jpg]

Highest
Quarter:

2Q ’20,

7.24%

Lowest
Quarter:

1Q ’22,

–6.43%

are shown for Class R5 only. After-tax returns for other classes will vary.

Average Annual Total Returns

(for the periods ended December 31, 2022)

		One Year			Five Years			Ten Years
Class R5	Return Before Taxes		-15.48	%		-0.06	%		1.58	%
	Return After Taxes on Distributions		-16.00	%		-1.49	%		0.20	%
	Return After Taxes on Distributions and Sales of Fund Shares		-9.15	%		-0.48	%		0.68	%
Class I	Return Before Taxes		-15.51	%		0.02	%		1.65	%
Service Class	Return Before Taxes		-15.66	%		-0.17	%		1.47	%
Administrative Class	Return Before Taxes		-15.69	%		-0.26	%		1.37	%
Class R4	Return Before Taxes		-15.84	%		-0.39	%		1.22	%
Class A	Return Before Taxes		-19.51	%		-1.39	%		0.67	%
Class R3	Return Before Taxes		-16.15	%		-0.68	%		0.94	%
Class Y	Return Before Taxes		-15.48	%		-0.06	%		1.58	%
Bloomberg U.S. Aggregate Bond Index (reflects no deduction for fees, expenses, or taxes)			-13.01	%		0.02	%		1.06	%

MANAGEMENT

Investment Adviser: MML Investment Advisers, LLC (“MML Advisers”)

Subadviser(s): Western Asset Management Company, LLC (“Western Asset”)

Western Asset Management Company Limited (“Western Asset Limited”)

Brandywine Global Investment Management, LLC (“Brandywine Global”)

Portfolio Manager(s):

John L. Bellows, CFA, PhD is a Portfolio Manager at Western Asset and Western Asset Limited. He has managed the Fund since February 2020.

S. Kenneth Leech is the Chief Investment Officer and a Portfolio Manager at Western Asset and Western Asset Limited. He has managed the Fund since March 2014.

Mark S. Lindbloom is a Portfolio Manager at Western Asset and Western Asset Limited.

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He has managed the Fund since December 2005.

Frederick R. Marki, CFA is a Portfolio Manager at Western Asset and Western Asset Limited. He has managed the Fund since February 2020.

Julien A. Scholnick, CFA is a Portfolio Manager at Western Asset and Western Asset Limited. He has managed the Fund since February 2020.

Tracy Chen, CFA, CAIA is a Portfolio Manager at Brandywine Global. She has managed the Fund since August 2021.

Brian Kloss, JD, CPA is a Portfolio Manager at Brandywine Global. He has managed the Fund since August 2021.

Jack McIntyre, CFA is a Portfolio Manager at Brandywine Global. He has managed the Fund since August 2021.

Anujeet Sareen, CFA is a Portfolio Manager at Brandywine Global. He has managed the Fund since August 2021.

PURCHASE AND SALE OF FUND SHARES

business day by written request, telephone, or internet (available to certain customers).

Purchase Minimums*

Class Y

Initial Investment

$100,000

Subsequent Investment

$250

The Fund reserves the right to change or waive the investment minimums. For retirement plans, the investment minimum is $250 for each of the initial investment and subsequent investments.

TAX INFORMATION

The Fund intends to make distributions that may be taxed as ordinary income, qualified dividend income, or capital gains, unless you are an investor eligible for preferential tax treatment.

PAYMENTS TO BROKER-DEALERS AND OTHER FINANCIAL INTERMEDIARIES

If you purchase the Fund through a broker-dealer or other financial intermediary, the intermediary may receive a one-time or continuing payments from the Fund, MML Advisers or its affiliates, or others for the sale of Fund shares or continuing shareholder services provided by the intermediary. These payments may create a conflict of interest by influencing the broker-dealer or other intermediary to recommend the Fund over another investment. You should contact your intermediary to obtain more information about the compensation it may receive in connection with your investment.

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MassMutual Diversified Value Fund

INVESTMENT OBJECTIVE

This Fund seeks to achieve long-term growth of capital and income by investing primarily in a diversified portfolio of equity securities of larger, well-established companies.

FEES AND EXPENSES OF THE FUND

Shareholder Fees (fees paid directly from your investment)

Class I

Class R5

Service
Class

Administrative
Class

Class R4

Class A

Class R3

Class Y

Maximum Sales Charge (Load) Imposed on Purchases (as a % of offering price)

None

5.50%

None

Maximum Deferred Sales Charge (Load) (as a % of the lower of the original offering price or redemption proceeds)

None

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your
investment)

	Class I	Class R5	Service Class	Administrative Class	Class R4	Class A	Class R3	Class Y
Management Fees	0.50%	0.50%	0.50%	0.50%	0.50%	0.50%	0.50%	0.50%
Distribution and Service (Rule 12b-1) Fees	None	None	None	None	0.25%	0.25%	0.50%	None
Other Expenses	0.08%	0.18%	0.28%	0.38%	0.28%	0.38%	0.28%	0.18%(1)
Total Annual Fund Operating Expenses	0.58%	0.68%	0.78%	0.88%	1.03%	1.13%	1.28%	0.68%

(1)

Other Expenses are based on estimated amounts for the current fiscal year of the Fund.

Example

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actual costs may be higher or lower, based on these assumptions your costs would be:

	1 Year			3 Years			5 Years			10 Years
Class I		$	59		$	186		$	324		$	726
Class R5		$	69		$	218		$	379		$	847
Service Class		$	80		$	249		$	433		$	966
Administrative Class		$	90		$	281		$	488		$	1,084
Class R4		$	105		$	328		$	569		$	1,259
Class A		$	659		$	889		$	1,138		$	1,849
Class R3		$	130		$	406		$	702		$	1,545
Class Y		$	69		$	218		$	379		$	847

Portfolio Turnover

INVESTMENTS, RISKS, AND PERFORMANCE

Principal Investment Strategies

The Fund invests primarily in stocks of companies that the subadvisers believe are undervalued in the marketplace. While the Fund does not limit its investments to issuers in a particular capitalization range, the subadvisers currently focus on securities of larger size companies. The Fund normally invests at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in stocks, securities convertible into stocks, and other securities, such as warrants and stock rights, whose value is based on stock prices. The Fund typically invests most of its assets in securities of U.S. companies, but may invest up to 25% of its total assets in foreign securities and American Depositary Receipts (“ADRs”), including emerging market securities. The Fund may use futures contracts for hedging or investment purposes as a substitute for investing directly in securities. Use of derivatives by the Fund may create investment leverage. The Fund is managed by two subadvisers, T. Rowe Price Associates, Inc. (“T. Rowe Price”) and Brandywine Global Investment Management, LLC (“Brandywine Global”), each being responsible for a portion of the portfolio, although they may manage different amounts of the Fund’s assets. The Fund may at

times have significant exposure to one or more industries or sectors. The Fund may hold a portion of its assets in cash or cash equivalents.

Brandywine Global invests in securities that meet its value criteria, primarily, price-to-earnings, price-to-book, price momentum, and share change and quality, based on both quantitative and fundamental analysis. Brandywine Global expects to hold approximately 175 – 250 stocks under normal market conditions.

Brandywine Global invests in securities of companies that meet its value criteria based on both quantitative and fundamental analysis. Brandywine Global’s investment process begins with a valuation screen that identifies large cap stocks with favorable financial ratios. A quantitative deselection process is then applied to eliminate equities that have poor price momentum or high share issuance. Finally Brandywine Global performs a thorough fundamental analysis which seeks to identify and eliminate (de-select) companies with deteriorating fundamentals, anticipated earnings declines, or material write-offs. Brandywine Global may also consider additional factors in its selection process.

Brandywine Global typically sells a security of a company when Brandywine Global believes it is no longer a large capitalization value company, if the company’s fundamentals deteriorate, when an investment opportunity arises that Brandywine Global believes is more compelling, or in order to realize gains or limit potential losses. However, Brandywine Global may retain securities of companies that no longer meet its initial purchase criteria.

T. Rowe Price typically employs a “value” approach in selecting investments, using internal research to identify companies that appear to be undervalued by various measures and may be temporarily out of favor but have good prospects for capital appreciation and dividend growth. T. Rowe Price generally looks for companies with one or more of the following: an established operating history; above-average dividend yield and low price/earnings ratio relative to the Russell 1000® Value Index; a sound balance sheet and other positive financial characteristics; and low stock price relative to T. Rowe Price’s view of the company’s underlying value as measured by assets, cash flow, or business franchises. T. Rowe Price generally seeks investments in large-capitalization companies and the yield of the portion of the Fund managed by T. Rowe Price is expected to

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normally exceed the yield of the Russell 1000 Value Index. T. Rowe Price may sell securities for a variety of reasons, including to realize gains, limit losses, or redeploy assets into more promising opportunities.

In pursuing the Fund’s investment objective, each of Brandywine Global and T. Rowe Price has the discretion to purchase some securities that do not meet its normal investment criteria described above, when it believes there is an opportunity for substantial appreciation (such as, for example, Brandywine Global or T. Rowe Price believes a security could increase in value as a result of a change in management, an extraordinary corporate event, a new product introduction or innovation, or a favorable competitive development).

Principal Risks

Equity Securities Risk Although stocks may have the potential to outperform other asset classes over the long term, their prices tend to fluctuate more dramatically over the shorter term. These movements may result from factors affecting individual companies, or from broader influences like changes in interest rates, market conditions, or investor confidence, or announcements of economic, political, or financial information.

may not have the effect or benefit anticipated. Derivatives can also reduce the opportunity for gains or result in losses by offsetting positive returns in other investments. Many derivatives are traded in the over-the-counter market and not on exchanges.

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securities issued in developed foreign markets, including less liquidity, less stringent investor protection and disclosure standards, less reliable settlement practices, greater price volatility, higher relative rates of inflation, greater political, economic, and social instability, greater custody and operational risks, greater risk of new or inconsistent government treatment of or restrictions on issuers and instruments, and greater volatility in currency exchange rates, and are more susceptible to environmental problems. Many emerging market countries are highly reliant on international trade and exports, including the export of commodities. Their economies may be significantly impacted by fluctuations in commodity prices and the global demand for certain commodities. In addition, pandemics and outbreaks of contagious diseases may exacerbate pre-existing problems in emerging market countries with less established health care systems. Frontier markets, a subset of emerging markets, generally have smaller economies and less mature capital markets than emerging markets. As a result, the risks of investing in emerging market countries are magnified in frontier market countries. Frontier markets are more susceptible to having abrupt changes in currency values, less mature markets and settlement practices, and lower trading volumes that could lead to greater price volatility and illiquidity. Non-U.S. transaction costs, such as brokerage commissions and custody costs, may be higher than in the United States. In addition, foreign markets can react differently to market, economic, industry, political, regulatory, geopolitical, public health, and other conditions than the U.S. market.

Large Company Risk Large-capitalization stocks as a group could fall out of favor with the market, causing the Fund’s investments in large-capitalization stocks to underperform investments that focus on small- or medium-capitalization stocks. Larger, more established companies may be slow to respond to challenges and may grow more slowly than smaller companies.

Value Company Risk The value investment approach entails the risk that the market will not recognize a security’s intrinsic value for a long time, or that a stock the investment adviser or subadviser judges to be undervalued may actually be appropriately priced.

Convertible Securities Risk Convertible securities are subject to the risks of both debt instruments and equity securities. The price of a convertible security may change in response to changes in price of the underlying equity security, the credit quality of the issuer, and interest rates. In general, the values of convertible securities tend to decline as interest rates rise and to rise when interest rates fall. A convertible security generally has less potential for gain or loss than the underlying equity security.

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Quantitative Models Risk The portfolio managers use quantitative models as part of the idea generation process. Quantitative models are based upon many factors that measure individual securities relative to each other. Such models may not produce the intended results and can be adversely affected by errors or imperfections in the factors or the data on which measurements are based, changing sources of market return or market risk, or any technical issues with the design, construction, implementation, or maintenance of the models.

Valuation Risk The Fund is subject to the risk of mispricing or improper valuation of its investments, in particular to the extent that its securities are fair valued.

Performance Information

Annual Performance

Class R5 Shares

[MISSING IMAGE: a6r64h9kotu045i6r07jujilehop.jpg]

Highest
Quarter:

4Q ’20,

16.46%

Lowest
Quarter:

1Q ’20,

–27.50%

After-tax returns are calculated using the historical highest individual U.S. federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns are not relevant to investors who hold Fund shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement accounts. After-tax returns are shown for Class R5 only. After-tax returns for other classes will vary.

Average Annual Total Returns

(for the periods ended December 31, 2022)

		One Year			Five Years			Ten Years
Class R5	Return Before Taxes		-2.19	%		7.68	%		10.99	%
	Return After Taxes on Distributions		-4.88	%		5.10	%		8.60	%
	Return After Taxes on Distributions and Sales of Fund Shares		0.70	%		5.66	%		8.62	%
Class I	Return Before Taxes		-2.10	%		7.78	%		11.07	%
Service Class	Return Before Taxes		-2.23	%		7.57	%		10.87	%
Administrative Class	Return Before Taxes		-2.45	%		7.45	%		10.76	%
Class R4	Return Before Taxes		-2.60	%		7.30	%		10.60	%
Class A	Return Before Taxes		-7.99	%		5.98	%		9.86	%
Class R3	Return Before Taxes		-2.81	%		7.01	%		10.29	%

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		One Year			Five Years			Ten Years
Class Y	Return Before Taxes		-2.19	%		7.68	%		10.99	%
Russell 1000 Value Index (reflects no deduction for fees, expenses, or taxes)			-7.54	%		6.67	%		10.29	%

MANAGEMENT

Investment Adviser: MML Investment Advisers, LLC (“MML Advisers”)

Subadviser(s): T. Rowe Price Associates, Inc. (“T. Rowe Price”)

Brandywine Global Investment Management, LLC (“Brandywine Global”)

Portfolio Manager(s):

John D. Linehan, CFA is a Vice President and Portfolio Manager at T. Rowe Price. He has managed the Fund since September 2017.

Joseph J. Kirby is a Portfolio Manager at Brandywine Global. He has managed the Fund since January 2010.

Henry F. Otto is a Managing Director and Portfolio Manager at Brandywine Global. He has managed the Fund since January 2010.

Steven M. Tonkovich is a Managing Director and Portfolio Manager at Brandywine Global. He has managed the Fund since January 2010.

PURCHASE AND SALE OF FUND SHARES

Shares of the Fund are generally available through distribution channels, such as broker-dealers or financial institutions, and to retirement plans, other

institutional investors, and individual retirement accounts. Fund shares are redeemable on any business day by written request, telephone, or internet (available to certain customers).

Purchase Minimums*

Class Y

Initial Investment

$100,000

Subsequent Investment

$250

The Fund reserves the right to change or waive the investment minimums. For retirement plans, the investment minimum is $250 for each of the initial investment and subsequent investments.

TAX INFORMATION

The Fund intends to make distributions that may be taxed as ordinary income, qualified dividend income, or capital gains, unless you are an investor eligible for preferential tax treatment.

PAYMENTS TO BROKER-DEALERS AND OTHER FINANCIAL INTERMEDIARIES

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MassMutual Fundamental Value Fund

INVESTMENT OBJECTIVE

The Fund seeks long-term total return.

FEES AND EXPENSES OF THE FUND

Shareholder Fees (fees paid directly from your investment)

Class I

Class R5

Service
Class

Administrative
Class

Class R4

Class A

Class R3

Class Y

Maximum Sales Charge (Load) Imposed on Purchases (as a % of offering price)

None

5.50%

None

Maximum Deferred Sales Charge (Load) (as a % of the lower of the original offering price or redemption proceeds)

None

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

	Class I	Class R5	Service Class	Administrative Class	Class R4	Class A	Class R3	Class Y
Management Fees	0.60%	0.60%	0.60%	0.60%	0.60%	0.60%	0.60%	0.60%
Distribution and Service (Rule 12b-1) Fees	None	None	None	None	0.25%	0.25%	0.50%	None
Other Expenses	0.06%	0.16%	0.26%	0.36%	0.26%	0.36%	0.26%	0.16%(1)
Total Annual Fund Operating Expenses	0.66%	0.76%	0.86%	0.96%	1.11%	1.21%	1.36%	0.76%

(1)

Other Expenses are based on estimated amounts for the current fiscal year of the Fund.

Example

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actual costs may be higher or lower, based on these assumptions your costs would be:

	1 Year			3 Years			5 Years			10 Years
Class I		$	67		$	211		$	368		$	822
Class R5		$	78		$	243		$	422		$	942
Service Class		$	88		$	274		$	477		$	1,061
Administrative Class		$	98		$	306		$	531		$	1,178
Class R4		$	113		$	353		$	612		$	1,352
Class A		$	667		$	913		$	1,178		$	1,935
Class R3		$	138		$	431		$	745		$	1,635
Class Y		$	78		$	243		$	422		$	942

Portfolio Turnover

INVESTMENTS, RISKS, AND PERFORMANCE

Principal Investment Strategies

The Fund invests primarily in equity securities of issuers that the Fund’s subadvisers believe are undervalued. The Fund is managed by two subadvisers, Boston Partners Global Investors, Inc. (“Boston Partners”) and Barrow, Hanley, Mewhinney & Strauss, LLC (“Barrow Hanley”), each being responsible for a portion of the portfolio, although they may manage different amounts of the Fund’s assets. Under normal circumstances, the Fund invests at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in equity securities. Equity securities may include common stocks, preferred stocks, securities convertible into common or preferred stocks, rights, and warrants. Although the Fund may invest in companies of any size, the Fund will tend to focus on companies with large market capitalizations (which the Fund’s subadvisers believe are generally above $1 billion). The Fund may invest up to 20% of its total assets in the securities of foreign issuers and American Depositary Receipts (“ADRs”), including emerging market securities. The Fund may invest up to 15% of its net assets in illiquid securities, including securities that are illiquid by virtue of the absence of a readily available market or legal or contractual

restrictions on resale. The Fund may participate as a purchaser in initial public offerings of securities (“IPOs”). An IPO is a company’s first offering of stock to the public. The Fund may at times have significant exposure to one or more industries or sectors. The Fund may hold a portion of its assets in cash or cash equivalents.

In selecting securities for the Fund, Boston Partners examines various factors to determine the value characteristics of such issuers, including price-to-book ratios and price-to-earnings ratios. These value characteristics are examined in the context of the issuer’s operating and financial fundamentals, such as return on equity, earnings growth, and cash flow. Boston Partners selects securities for the Fund based on a continuous study of trends in industries and companies, earnings power, growth, and other investment criteria. Boston Partners will sell a security when it no longer meets one or more investment criteria, either through obtaining target value or due to an adverse change in the fundamentals or business momentum. Each holding has a target valuation established at purchase, which Boston Partners continuously monitors and adjusts as appropriate.

Barrow Hanley employs a value-based investment approach and may perform a number of analyses in considering whether to buy or sell a security for the Fund. In selecting investments for the Fund, Barrow Hanley typically seeks to exploit market inefficiencies by using proprietary research to identify primarily large capitalization companies that it considers to be undervalued and to have the potential to generate superior returns while subjecting the Fund to below average levels of risk. Barrow Hanley typically invests in approximately 75–100 securities. Barrow Hanley may consider selling a stock for the Fund if, in its judgment, the security has reached its valuation target, the company’s fundamentals begin to deteriorate, or other opportunities appear more attractive.

Principal Risks

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are less liquid and at times more volatile than securities of comparable U.S. companies. Emerging markets securities are subject to greater risks than securities issued in developed foreign markets, including less liquidity, less stringent investor protection and disclosure standards, less reliable settlement practices, greater price volatility, higher relative rates of inflation, greater political, economic, and social instability, greater custody and operational risks, greater risk of new or inconsistent government treatment of or restrictions on issuers and instruments, and greater volatility in currency exchange rates, and are more susceptible to environmental problems. Many emerging market countries are highly reliant on international trade and exports, including the export of commodities. Their economies may be significantly impacted by fluctuations in commodity prices and the global demand for certain commodities. In addition, pandemics and outbreaks of contagious diseases may exacerbate pre-existing problems in emerging market countries with less established health care systems. Frontier markets, a subset of emerging markets, generally have smaller economies and less mature capital markets than emerging markets. As a result, the risks of investing in emerging market countries are magnified in frontier market countries. Frontier markets are more susceptible to having abrupt changes in currency values, less mature markets and settlement practices, and lower trading volumes that could lead to greater price volatility and illiquidity. Non-U.S. transaction costs, such as brokerage commissions and custody costs, may be higher than in the United States. In addition, foreign markets can react differently to market, economic, industry, political, regulatory, geopolitical, public health, and other conditions than the U.S. market.

Small and Mid-Cap Company Risk Market risk and liquidity risk are particularly pronounced for securities of small and medium-sized companies, which may trade less frequently and in smaller volumes than more widely-held securities, and may fluctuate in price more than other securities. Their shares can be less liquid than those of larger

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companies, especially during market declines. Small and medium-sized companies may have limited product lines, markets, or financial resources and may be dependent on a limited management group; they may have been recently organized and have little or no track record of success.

Market Risk The value of the Fund’s portfolio securities may decline, at times sharply and unpredictably, as a result of unfavorable market-induced changes affecting particular industries,

sectors, or issuers. Stock and bond markets can decline significantly in response to issuer, market, economic, industry, political, regulatory, geopolitical, public health, and other conditions, as well as investor perceptions of these conditions. The Fund is subject to risks affecting issuers, such as management performance, financial leverage, industry problems, and reduced demand for goods or services.

Preferred Stock Risk Like other equity securities, preferred stock is subject to the risk that its value may decrease based on actual or perceived changes in the business or financial condition of the issuer. In addition, changes in interest rates may adversely affect the value of a preferred stock that pays a fixed dividend. Preferred stocks are also subject to additional risks, such as potentially greater volatility and risks related to deferral, non-cumulative dividends, subordination, liquidity, limited voting rights, and special redemption rights.

Valuation Risk The Fund is subject to the risk of mispricing or improper valuation of its investments, in particular to the extent that its securities are fair valued.

Performance Information

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performance of Class R5 shares, adjusted for Class R4 shares to reflect Class R4 expenses. Performance for Class A shares of the Fund reflects any applicable sales charge. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. More up-to-date performance information is available at https://www.massmutual.com/funds or by calling 1-888-309-3539.

Annual Performance

Class R5 Shares

[MISSING IMAGE: mklp77famb8q2jslgb53njncgreg.jpg]

Highest
Quarter:

4Q ’20,

19.59%

Lowest
Quarter:

1Q ’20,

–29.95%

After-tax returns are calculated using the historical highest individual U.S. federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns are not relevant to investors who hold Fund shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement accounts. After-tax returns are shown for Class R5 only. After-tax returns for other classes will vary.

Average Annual Total Returns

(for the periods ended December 31, 2022)

		One Year			Five Years			Ten Years
Class R5	Return Before Taxes		-2.78	%		6.92	%			9.99	%
	Return After Taxes on Distributions		-6.12	%		3.77	%			6.90	%
	Return After Taxes on Distributions and Sales of Fund Shares		0.79	%		5.03	%			7.55	%
Class I	Return Before Taxes		-2.58	%		7.04	%			10.12	%
Service Class	Return Before Taxes		-2.77	%		6.83	%		R

	Page
About the Funds
MassMutual Total Return Bond Fund		3
MassMutual Strategic Bond Fund		12
MassMutual Diversified Value Fund		20
MassMutual Fundamental Value Fund		26
MM S&P 500® Index Fund		32
MassMutual Equity Opportunities Fund		36
MassMutual Fundamental Growth Fund		42
MassMutual Blue Chip Growth Fund		48
MassMutual Growth Opportunities Fund		54
MassMutual Mid Cap Value Fund		60
MassMutual Small Cap Value Equity Fund		68
MassMutual Small Company Value Fund		73
MassMutual Mid Cap Growth Fund		79
MassMutual Small Cap Growth Equity Fund		85
MassMutual Overseas Fund		91
MassMutual Select T. Rowe Price International Equity Fund		97
Additional Information Regarding Investment Objectives and Principal Investment Strategies		104
Disclosure of Portfolio Holdings		107
Additional Information Regarding Principal Risks		107
Management of the Funds
Investment Adviser		126
Subadvisers and Portfolio Managers		126
About the Classes of Shares – I, R5, Service, Administrative, R4, A, R3, and Y Shares		140
Sales Charges by Class		142
Sales Charge Waivers by Class		143
Distribution Plan, Shareholder Servicing, and Payments to Intermediaries		144
Buying, Redeeming, and Exchanging Shares		146
Cost Basis Reporting		149
Frequent Trading Policies		150
Determining Net Asset Value		151
Taxation and Distributions		152
Financial Highlights		155
Index Descriptions		172