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, 2026
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:
Banco Santander,
S.A.
TABLE OF CONTENTS
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Report of Other Relevant
Information dated August 5, 2026 |
Item
1

Banco Santander, S.A. (“Banco Santander”
or the “Bank”), in compliance with the Securities Market legislation, hereby announces the following:
OTHER RELEVANT INFORMATION
Further to the inside information notice
dated 3 February 2026 (registry number 3071) and the other relevant information notice dated 23 April 2026 (registry number 40405),
concerning the acquisition of Webster Financial Corporation (the “Acquisition”), the Bank hereby informs that,
after having obtained the approval from the Office of the Comptroller of the Currency on 12 June 2026 and the authorisation from the
European Central Bank on 21 July 2026, on 4 August 2026, it received the approval from
the Board of Governors of the Federal Reserve System of the United States required to complete the Acquisition on the terms
previously announced. The completion of the Acquisition is expected to occur on 20 August 2026.
Boadilla del Monte (Madrid), 5 August 2026

FORWARD-LOOKING STATEMENTS
This communication contains statements that constitute
“forward-looking statements” within the meaning of, and subject to the protections of, Section 27A of the Securities Act of
1933, as amended (the “Securities Act”), and Section 21E of the Securities Exchange Act of 1934, as amended, and the safe
harbor provisions of the U.S. Private Securities Litigation Reform Act of 1995. Forward-looking statements can be identified by words
such as “achieve,” “anticipate,” “assume,” “believe,” “could,” “deliver,”
“drive,” “enhance,” “estimate,” “expect,” “focus,” “future,” “goal,”
“grow,” “guidance,” “intend,” “may,” “might,” “plan,” “position,”
“potential,” “predict,” “project,” “opportunity,” “outlook,” “should,”
“strategy,” “target,” “trajectory,” “trend,” “will,” “would,”
and other similar words and expressions or the negative of such terms or other comparable terminology. Forward-looking statements include,
but are not limited to, statements about business strategy, goals and objectives, projected financial and operating results, including
outlook for future growth, and future share dividends, share repurchases and other uses of capital. These statements are not historical
facts, but instead represent our beliefs regarding future events, many of which, by their nature, are inherently uncertain and outside
of our control. As forward-looking statements involve significant risks and uncertainties, readers are cautioned not to place undue reliance
on such statements.
Webster Financial Corporation’s (“Webster”) and Banco
Santander S.A.’s (“Banco Santander”) actual results, financial condition and achievements may differ materially from
those indicated in these forward-looking statements. Important factors that could cause Webster’s and Banco Santander’s actual
results, financial condition and achievements to differ materially from those indicated in such forward-looking statements include, in
addition to those set forth in Webster’s and Banco Santander’s filings with the U.S. Securities and Exchange Commission (the
“SEC”): (1) the risk that the cost savings, synergies and other benefits from the acquisition of Webster by Banco Santander
(the “Transaction”) may not be fully realized or may take longer than anticipated to be realized, including as a result of
changes in, or problems arising from, general economic and market conditions, interest and exchange rates, monetary policy, laws and
regulations and their enforcement, and the degree of competition in the geographic and business areas in which Webster and Banco Santander
operate; (2) the failure of the closing conditions in the Transaction agreement by and among Webster, Banco Santander and a wholly-owned
subsidiary of Webster providing for the Transaction to be satisfied, or any unexpected delay in closing the Transaction or the occurrence
of any event, change or other circumstances that could delay the Transaction or could give rise to the termination of the Transaction
agreement; (3) the outcome of any legal or regulatory proceedings or governmental inquiries or investigations that may be currently pending
or later instituted against Webster, Banco Santander or the combined company; (4) the possibility that the Transaction does not close
when expected or at all because the remaining conditions to closing are not received or satisfied on a timely basis or at all; (5) disruption
to the parties’ businesses as a result of the announcement and pendency of the Transaction; (6) the costs associated with the anticipated
length of time of the pendency of the Transaction, including the restrictions contained in the definitive Transaction agreement on the
ability of Webster to operate its business outside the ordinary course during the pendency of the Transaction; (7) risks related to management
and oversight of the expanded business and operations of the combined company following the closing
of the proposed Transaction; (8) the risk that the integration of Webster’s
operations with Banco Santander’s will be materially delayed or will be more costly or difficult than expected or that the parties
are otherwise unable to successfully integrate each party’s businesses into the other’s businesses; (9) the possibility that
the Transaction may be more expensive to complete than anticipated, including as a result of unexpected factors or events; (10) reputational
risk and potential adverse reactions of Webster’s or Banco Santander’s customers, employees, vendors, contractors or other
business partners, including those resulting from the announcement or completion of the Transaction; (11) the dilution caused by Banco
Santander’s issuance of additional ordinary shares and corresponding American depositary shares, each representing the right to
receive one of its ordinary shares (“ADSs”), in connection with the Transaction; (12) the possibility that any announcements
relating to the Transaction could have adverse effects on the market price of Webster’s common stock and Banco Santander’s
ordinary shares and ADSs; (13) a material adverse change in the condition of Webster or Banco Santander; (14) the extent to which Webster’s
or Banco Santander’s businesses perform consistent with management’s expectations; (15) Webster’s and Banco Santander’s
ability to take advantage of growth opportunities and implement targeted initiatives in the timeframe and on the terms currently expected;
(16) the inability to sustain revenue and earnings growth; (17) the execution and efficacy of recent strategic investments; (18) the impact
of global conditions (e.g., an economic downturn; higher volatility in the capital markets; inflation; deflation; changes in demographics,
consumer spending, investment or saving habits; and the effects of the wars in Ukraine and in the Middle East or other hostilities or
the outbreak of public health emergencies on the global economy) and monetary and fiscal policy, particularly on interest rates; (19)
changes in customer behavior; (20) unfavorable developments concerning credit quality; (21) declines in the businesses or industries of
Webster’s or Banco Santander’s customers; (22) the possibility that the combined company is subject to additional regulatory
requirements as a result of the proposed Transaction or expansion of the combined company’s business operations following the proposed
Transaction; (23) general competitive, political and market conditions and other factors that may affect future returns of Webster and
Banco Santander, including changes in asset quality and credit risk; (24) security risks, including cybersecurity and data privacy risks,
and capital markets; (25) inflation; (26) the impact, extent and timing of technological changes; (27) capital management activities;
(28) competitive product and pricing pressures; (29) the outcomes of legal and regulatory proceedings and related financial services industry
matters; and (30) compliance with regulatory requirements. Any forward-looking statement made in this communication is based solely on
information currently available to us and speaks only as of the date on which it is made.

Webster and Banco Santander undertake no
obligation to publicly update any forward-looking statement, whether written or oral, that may be made from time to time, whether as
a result of new information, future developments or otherwise, except to the extent required by law. These and other
important factors, including those discussed under “Risk Factors” in Webster’s Annual Report on Form 10-K for the
year ended December 31, 2025, as amended (available at:
https://www.sec.gov/ix?doc=/Archives/edgar/data/0000801337/000080133726000008/wbs-20251231.htm and https://www.sec.gov/ix?doc=/Archives/edgar/data/
0000801337/000080133726000011/wbs-20251231.htm), and Banco Santander’s Annual Report on Form 20-F for the year ended
December 31, 2025 (available at: https://www.sec.gov/ix?doc=/Archives/edgar/data/0000891478/000089147826000030/san-20251231.htm),
as well as Webster’s and Banco Santander’s subsequent filings with the SEC, may cause actual results, performance or
achievements to differ materially from those expressed or implied by these forward-looking statements. The forward-looking
statements herein are made only as of the date they were first issued, and unless otherwise required by applicable securities laws,
Webster and Banco Santander disclaim any intention or obligation to update or revise any forward-looking statements, whether as a
result of new information, future events, or otherwise.
NO OFFER OR SOLICITATION
This communication does not constitute an offer
to sell or the solicitation of an offer to buy any securities or a solicitation of any vote or approval, nor shall there be any sale
of securities in any jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification
under the securities laws of any such jurisdiction. No offer of securities shall be made except by means of a prospectus meeting the
requirements of Section 10 of the Securities Act. No investment activity should be undertaken on the basis of the information contained
in this communication. By making this communication available, no advice or recommendation is being given to buy, sell or otherwise deal
in any securities or investments whatsoever.
SIGNATURE
Pursuant to the
requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned,
thereunto duly authorized.
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Banco Santander, S.A. |
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| Date: |
August 5, 2026
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By: |
/s/ Pedro de Mingo Kaminouchi |
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Name: |
Pedro de Mingo Kaminouchi |
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Title: |
Head of Corporate Compliance |