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FORM 6-K

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Report of Foreign Issuer

Pursuant to Rule 13a-16 or 15d-16 of

the Securities Exchange Act of 1934

For the month of August, 2015

Commission File Number: 001-12518

Banco Santander, S.A.

(Exact name of registrant as specified in its charter)

Ciudad Grupo Santander

28660 Boadilla del Monte (Madrid) Spain

(Address of principal executive office)

Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F:

Form 20-F  x            Form 40-F  ¨

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(1):

Yes  ¨            No   x

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(7):

Yes  ¨            No   x

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Banco Santander, S.A.

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INCORPORATION BY REFERENCE

Items 2 and 3 of this report on Form 6-K shall be deemed to be incorporated by reference into the registration statement on Form F-3 (Registration Number: 333-185153) of Banco Santander, S.A. and to be a part thereof from the date on which this report is filed, to the extent not superseded by documents or reports subsequently filed or furnished.

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Item 1

PRESS RELEASE

FIRST HALF 2015 RESULTS

Santander made ordinary profit of EUR 3.426

billion, a 24% increase

Madrid, July 30, 2015. Banco Santander made an ordinary attributable profit of EUR 3,426 million in the first half, 24% more than the same period last year. Santander’s ten core markets increased profit, with a particularly important increase in the bank’s three largest markets: Spain, United Kingdom and Brazil.

Comunicación Externa.		1
Ciudad Grupo Santander Edificio Arrecife Pl. 2
28660 Boadilla del Monte (Madrid) Telf.: 34 91 289 52 11
email: [email protected]

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Results

In the first half of 2015, Santander registered notable growth in business and revenues, which also benefited from exchange rates, particularly the euro-dollar and euro-pound depreciation. Business and revenue grew more than 12%, 7% without the exchange rate effect, which together with the reduction in loan loss provisions by 5% (9% without the exchange rate effect) brought an improvement in the ordinary attributable profit of 24% in the first half of the year. Growth would have been 16% without the exchange rate effect.

These results are produced in a context of uneven economic performance for the different countries in which the group operates. Countries such as Spain, U.S. and Poland are expected to grow more than 3% this year; U.K., Mexico and Chile, more than 2.5%, and Germany and Portugal, over 1.5%. Meanwhile, Brazil and Argentina will register a fall in economic activity. Official interest rates in euros, dollars and pounds continue to be at historic lows.

The improvement in profits is a result of an increase in revenues of 12%, a variation of one point greater than costs, which grew 11%. This performance allows continued improvement in the efficiency ratio of 0.6 point, to 46.9%, which positions Banco Santander among the most efficient financial institutions in the world.

Net operating income, the difference between income and costs, stood at EUR 12,256 million, with growth of 13%. This increase, together with the decrease in loan loss provisions of 5%, means that the ordinary attributable profit amounted to EUR 3,426 million, an increase of 24%. That figure does not include the EUR 835 million from the reversal of tax liabilities in Brazil, which allowed the bank to strengthen its capital ratios.

Comunicación Externa.		2
Ciudad Grupo Santander Edificio Arrecife Pl. 2
28660 Boadilla del Monte (Madrid) Telf.: 34 91 289 52 11
email: [email protected]

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Emerging economies (Latin America and Poland) accounted for 41% of profit and mature markets contributed 59%. By country, the largest contribution was from U.K. (21%), followed by Brazil (20%), Spain (16%), U.S. (9%), Mexico (7%), Chile (5%), Poland and Argentina (4% each) and Portugal (2%). Santander Consumer Finance contributed 10% to total profit.

Balance sheet

Banco Santander closed June 2015 with total assets of EUR 1.339 trillion, 13% more than June 2014. The business shows balanced growth, since new loans grew 13% and customer funds (deposits plus mutual funds), 12%.

At the end of June 2015, the loan portfolio reached EUR 826,707 million, 13% more than the year before (7% without the exchange rate effect). In the first half of the year, lending rose EUR 65,000 million.

In Spain, the total loan portfolio reached EUR 161,357 million, virtually the same as at the end of June 2014, after subtracting repos. New lending to companies grew 17% and to individuals, 33%, with mortgages increasing 29%. In the first half of the year, Santander provided EUR 6,218 million in financing to SMEs and micro-enterprises, 28% more than a year earlier. The increase in new lending to companies allows growth in final balances, while mortgage repayments exceeded new transactions.

In U.K., the loan portfolio stood at EUR 283,740 million, with growth of 18% over the first half of 2014. Without the exchange rate effect, in pounds, the increase in lending was 5%, boosted by financing to companies, which grew 11% year-on-year; mortgages, up 1%, and consumer and auto finance, which increased 48%.

Comunicación Externa.		3
Ciudad Grupo Santander Edificio Arrecife Pl. 2
28660 Boadilla del Monte (Madrid) Telf.: 34 91 289 52 11
email: [email protected]

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In Brazil, the loan portfolio reached EUR 75,902 million, growing 16%, but remaining flat when converted to euros. Financing to companies was responsible for most of the growth, 23%, as well as in mortgages, which increased 34%. Financing to SMEs also showed marked improvement, and grew 6% year-on-year.

As for customer funds, total deposits and mutual funds of the bank were EUR 823,482 million, with growth of 12% (8% without the exchange rate effect), which represents an addition of EUR 51,000 million in one year. Deposits reached 687,900 million and mutual funds 135,582 million, with growth of 11% and 13%, respectively, year-on-year. All markets gained customer funds.

Current accounts, which make up nearly two thirds of deposits, showed positive growth in the group’s ten key markets. The current account balance reached EUR 413,000 million at the close of the first half of the year, with growth of 27% compared with the end of June 2014. This means that in twelve months, a gain of EUR 89,000 million was added to these accounts. The current account is key to the strategy of increasing the loyalty of the bank’s customers, since it is the conduit for most transactions, centralizing income and expenses. For this reason, last May Santander rolled out in Spain the 1|2|3 Account, a fidelity and customer relationship strategy that was launched three years ago in U.K. and is also the focus of the strategy in Portugal starting this year.

In Spain, total customer funds (deposits plus mutual funds) amounted to EUR 227,187 million at the end of June of this year, with an increase of 6% for the last twelve months. Demand deposits grew 20%, compared to a fall of 19% for time deposits, and assets in mutual funds rose 17%. This strategy reduced the cost of deposits by half a point in a year.

Comunicación Externa.		4
Ciudad Grupo Santander Edificio Arrecife Pl. 2
28660 Boadilla del Monte (Madrid) Telf.: 34 91 289 52 11
email: [email protected]

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In U.K., the volume of deposits plus mutual funds reached EUR 232,883 million and grew 17% for the year, 4% without the exchange rate effect. This increase accelerated in the last quarter and the strategy continues to focus on current accounts to individuals, the balance of which increased 36% in twelve months, with a rate of increase of one billion pounds per month. The 1|2|3 strategy has attracted 4.3 million customers, 1.3 million in the last twelve months, and for 95% of them, Santander is their primary bank.

In Brazil, the total of deposits and mutual funds reached EUR 89,379 million, with growth of 13% without the exchange rate effect, and flat when converted from Brazilian real to euros. Total deposits grew 9% and funds, 16%.

Spain, U.K. and Brazil represented 70% of customer funds managed and commercialised by the group and 64% of the loan portfolio. Loan portfolio quality continued to improve significantly in Spain and U.K., while the non-performing loans grew in Brazil in the quarter, but they are still far from last year’s figures. The group’s non-performing loans stood at 4.64% at the close of the first half of the year, with a decrease of 0.81 point in one year.

Net entries of non-performing loans were EUR 1,315 million in the second quarter of this year, approximately half of the quarterly average last year. At the same time, the group continues to raise coverage, which already stands at 70%, compared to 67% a year ago.

Capital

At the beginning of the year, the bank carried out a rights issue for EUR 7,500 million via an accelerated bookbuilding offer to institutional investors. At the close of the first half of the year, Banco Santander’s total equity stood at EUR 91,497 million and the capital ratios improved in the quarter. The bank’s total fully loaded capital ratio grew 0.34 point, to 12.37%, and the fully loaded core capital ratio grew 0.16 point, to 9.83%.

Comunicación Externa.		5
Ciudad Grupo Santander Edificio Arrecife Pl. 2
28660 Boadilla del Monte (Madrid) Telf.: 34 91 289 52 11
email: [email protected]

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Earnings per share for the first half of this year was 0.2% higher than last year thanks to the fact that, although the number of shares increased by 22% as a result of the capital increase and the script dividend, profit grew 24%. The return on tangible equity (ROTE) increased by 0.6 point, to 11.5%.

Along with the rights issue, the bank’s board of directors announced its new dividend policy against fiscal year 2015, which consists of the payment of four dividends for EUR 0.05 per share, of which three will be paid in cash and one in shares or cash, per the shareholders choice. This year’s August dividend payment will be made entirely in cash.

Banco Santander has a market capitalization of more than EUR 90,000 million, making it the first bank in the euro zone and eleventh-largest in the world. Santander has 3,203,349 shareholders and 190,262 employees serving over 110 million customers through 12,910 branches.

More information at www.santander.com

Comunicación Externa.		6
Ciudad Grupo Santander Edificio Arrecife Pl. 2
28660 Boadilla del Monte (Madrid) Telf.: 34 91 289 52 11
email: [email protected]

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 KEY CONSOLIDATED DATA 

Variations w/o exchange rate

Quarterly: Net interest income: +3.6%; Gross income: +2.1%; Pre-provision profit: +2.8%; Attributable profit: -0.2%

Year-on-year: Net interest income: +8.0%; Gross income: +6.9%; Pre-provision profit: +7.4%; Attributable profit: +15.6%

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Item 2

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Financial report

At Banco Santander, we take advantage of new

communication technologies and the social

networks to improve dialogue with our

stakeholders

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KEY CONSOLIDATED DATA

Variations w/o exchange rate

Quarterly: Net interest income: +3.6%; Gross income: +2.1%; Pre-provision profit: +2.8%; Attributable profit: -0.2%

Year-on-year: Net interest income: +8.0%; Gross income: +6.9%; Pre-provision profit: +7.4%; Attributable profit: +15.6%

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Best bank for our employees				Best bank for our customers
Attract, engage and retain the best talent, capable of providing the best service to our customers and guarantee the business success and sustainability.				Build long-term customer relationships providing simple and tailor-made solutions, a fair and equal treatment and excellent service in our branches and digital channels, in order to enhance their satisfaction and engagement with the Bank.
Best bank for communities				Best bank for our shareholders
Conduct our banking activity contributing to the economic and social progress of the communities in which we operate, in a responsible and sustainable way, and particularly committed to the field of higher education.				Generate an attractive and sustainable return for our shareholders based on a business model with a high degree of recurring revenues, prudent risks, efficient, with disciplined use of capital and financial strength.

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Simple | Personal | Fair

The Human Resources Strategic Plan, which responds to the needs of the new culture and contributes to the rest of the Group’s strategic lines, began to be implemented. Of note among the main points are:

Transforming our business model into one that is more personalised and modern continues, in order to enhance customer satisfaction and loyalty:

The Bank continued to advance in strengthening its many channels with new and better commercial websites, new applications and functions for mobile phones, including Apple Pay in the UK, Santander Watch in Spain and the new Deposit Capture in the US.

We continued to develop initiatives to improve transparency with our shareholders and facilitate the exercise of their rights. Of note in the second quarter were:

As part of its commitment to society, of note in the second quarter were:

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General background

Despite market volatility during the second quarter because of the Greek crisis, Grupo Santander conducted its business in an environment of growth in most of the countries where it operates.

Growth remained firm in the US and UK, and the euro zone recovery continued to strengthen.

Among the emerging economies, Brazil continued to be affected by adjustment policies. Mexico and Chile, however, gained momentum and Poland maintained satisfactory growth.

The US economy slowed down in the first quarter largely due to temporary factors and in the second quarter regained the path of expansion, though growth was softer than in the last quarter of 2014. This resulted in a downgrade in growth for the year (2.5%). Inflation was still below the Federal Reserve’s target, but the trend is slightly upward. The Fed could raise its interest rates this year, though the market’s most probable scenario is this does not happen until the fourth quarter.

Latin American economies had an uneven performance:

In order to reinforce its anti-inflation commitment, the central bank narrowed its target range from +/-2% (2.5-6.5%) to +/-1.5% (3-6%). Although the inflation rate rose in June to 8.9%, the expectations remain stable for 2016 (5.5%) and around 4.5% for 2017.

After depreciating 20% against the dollar in the first quarter, the real appreciated 5% in the second quarter, reflecting tinvestors’ greater confidence in Brazil’s monetary and fiscal policies and its commitment to macroeconomic stability. The real appreciated 1% against the euro in the second quarter.

The euro zone gained momentum in the first quarter. The pace of growth accelerated from 0.3% quarter-on-quarter to 0.4% (from 0.9% to 1.0% year-on-year). These figures reflect a general trend of improvement, with higher consumption (oil price impact).

The second quarter indicators point to a similar rate of recovery. Inflation remains very low (0.2% in June) but has begun an upward trend after exiting negative rates. The European Central Bank is committed to maintaining its quantitative-easing programme until at least September 2016.

United Kingdom: GDP rose 0.4% quarter-on-quarter in the first quarter, slightly below the growth in the fourth quarter and in an environment in which the impact of oil prices on consumption was more than compensated by weak exports due to the currency’s appreciation. Inflation was around 0%, although the rise in salaries makes it likely that this will be short lived and prices will rise during the second half of the year.

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Poland: GDP grew 1% quarter-on-quarter in the first quarter (seasonally adjusted) and 3.6% year-on-year. Activity is gaining strength and deflation is beginning to abate. Macroeconomic fundamentals are under control and policies well focused. The central bank lowered its benchmark rate (1.5%) and announced the end of the cycle of cuts, given the zloty’s stability.

Banking business continued to be affected by interest rates at an all-time low in most countries and tougher competition in some markets, mainly on the assets side, and a demanding regulatory environment.

Exchange rates: 1 euro / currency parity

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u Grupo Santander results

First half highlights

Ordinary income statement EUR Million