Publication of a Supplementary Prospectus

THIRD SUPPLEMENT DATED 20 APRIL 2026TO THE BASE PROSPECTUS DATED 18 JULY 2025

NATIXIS

(a public limited liability company (société anonyme) incorporated in France)

as Issuer and Guarantor

and

NATIXIS STRUCTURED ISSUANCE SA (a public limited liability company (société anonyme) incorporated under the laws of the Grand Duchy ofLuxembourg)as Issuer

£1,000,000,000 UK Debt Issuance Programme

This base prospectus supplement (the "Supplement" or the "Third Supplement") is supplemental to and must be read in conjunction with the base prospectus dated 18 July 2025, as supplemented by the first supplement dated 17 September 2025 and the second supplement dated 25 November 2025 (together, the "Base Prospectus"), relating to the UK Debt Issuance Programme of NATIXIS ("NATIXIS") and Natixis Structured Issuance SA ("Natixis Structured Issuance" and together with NATIXIS, the "Issuers" and each an "Issuer"), prepared in connection with the application made for the Notes to be admitted to listing on the Official List of the United Kingdom Financial Conduct Authority (the "FCA") (in its capacity as competent authority for the purposes of Part VI of the Financial Services and Markets Act 2000 (the "FSMA")), and to trading on the main market of the London Stock Exchange plc.

This Third Supplement constitutes a supplement for the purposes of Regulation (EU) 2017/1129 as it forms part of domestic law in the United Kingdom by virtue of the European Union (Withdrawal) Act 2018, as amended (the "UK Prospectus Regulation") and a supplementary prospectus for the purposes of section 87G of the FSMA. Terms defined in the Base Prospectus shall have the same meaning when used in this Third Supplement. This Third Supplement has been approved by the FCA as competent authority under the UK Prospectus Regulation. The FCA only approves this Third Supplement as meeting the standards of completeness, comprehensibility and consistency imposed by the UK Prospectus Regulation. Such approval should not be considered as an endorsement of the Issuer that is the subject of this Third Supplement. With effect from the date of this Third Supplement the information appearing in, or incorporated by reference into, the Base Prospectus shall be supplemented in the manner described below.

This Third Supplement will be published on the website of the Regulatory News Service operated by the London Stock Exchange (https://www.londonstockexchange.com/news?tab=news-explorer&period=daily&headlinetypes=1,2 and on the Issuers' website  (https://cib.natixis.com/Home/pims/Prospectus#/prospectusPublic).

Unless the context otherwise requires, terms defined in the Base Prospectus shall have the same meaning when used in this Third Supplement.

Save as disclosed in this Third Supplement, no significant new factor, material mistake or material inaccuracy relating to information included in the Base Prospectus has arisen since the publication of the Base Prospectus. To the extent that there is any inconsistency between (a) any statement in this Third Supplement or any statement

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incorporated by reference into the Base Prospectus by this Third Supplement and (b) any other statement in or incorporated by reference in the Base Prospectus, the statements in this Third Supplement will prevail.

The Issuers accept responsibility for the information contained or incorporated by reference in this Third Supplement. To the best of the knowledge of the Issuers, the information contained or incorporated by reference in this Third Supplement is in accordance with the facts and does not omit anything likely to affect its import.

This Third Supplement has been prepared for the purposes of:

a) incorporating by reference into the Base Prospectus the 2025 universal registration document and annual financial report of NATIXIS, being a free English translation of the document d'enregistrement universel 2025 et rapport financier annuel that has been filed with the French Autorité des marchés financiers on 18 March 2026 under number D.26-0109 (the "NATIXIS 2025 Universal Registration Document");

b) incorporating by reference into the Base Prospectus Natixis Structured Issuance's audited annual financial statements for the financial year ended 31 December 2025 (the "NSI 2025 Annual Accounts"); and

c) amending, as a result of a) and b) above, the following sections of the Base Prospectus: "RISK FACTORS", "DOCUMENTS INCORPORATED BY REFERENCE", "DESCRIPTION OF THE ISSUERS" and "GENERAL INFORMATION".

To the extent applicable, investors who have already agreed to purchase or subscribe for any Notes before this Third Supplement is published, have the right, exercisable within a time limit of three (3) working days after the publication of this Third Supplement (no later than 23 April 2026), to withdraw their acceptances, provided that the significant new factor, material mistake or material inaccuracy arose or was noted before the closing of the offer period or the delivery of the Notes. Investors may contact the Authorised Offerors should they wish to exercise the right of withdrawal.

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Appendix 1

RISK FACTORS

From the date of this Third Supplement, the sub-section 1.1 "Risks relating to NATIXIS as Issuer or Guarantor" (appearing on page 19 of the Base Prospectus) of the section "RISK FACTORS" of the Base Prospectus shall be deleted in its entirety and replaced as follows:

"1.1 Risks relating to NATIXIS as Issuer or Guarantor

The risk factors associated to NATIXIS that may affect NATIXIS' ability to perform its obligations either as Issuer or as Guarantor under the Notes issued pursuant to the Programme are described in the "Risk Factors" section on pages 93 to 104 of the NATIXIS 2025 Universal Registration Document, which is incorporated by reference herein.

The following subsections of the above-mentioned section are incorporated by reference in this category of risk factors:

· Credit and counterparty risks;

· Financial risks;

· Non-financial risks; and

· Strategic and business risks."

Appendix 2

DOCUMENTS INCORPORATED BY REFERENCE

From the date of this Third Supplement, the section entitled "DOCUMENTS INCORPORATED BY REFERENCE" (appearing on pages 61 to 68 of the Base Prospectus) is deleted in its entirety and replaced as follows:

"DOCUMENTS INCORPORATED BY REFERENCE

The pages identified in the cross-reference tables below of the following documents, which have been previously published or are published simultaneously with the Base Prospectus and have been filed with the FCA shall be incorporated by reference in, and form part of, this Base Prospectus.

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The non-incorporated parts of the documents incorporated by reference are either not relevant for investors or covered elsewhere in this Base Prospectus. For the avoidance of doubt, any documents themselves incorporated by reference in the documents incorporated by reference in this Base Prospectus shall not form part of this Base Prospectus.

Following the publication of this Base Prospectus a supplement may be prepared by the relevant Issuer and approved by the FCA in accordance with Article 23 of the UK Prospectus Regulation. Statements contained in any such supplement (or contained in any document incorporated by reference therein) shall, to the extent applicable (whether expressly, by implication or otherwise), be deemed to modify or supersede statements contained in this Base Prospectus or in a document which is incorporated by reference in this Base Prospectus. Any statement so modified or superseded shall not, except as so modified or superseded, constitute a part of this Base Prospectus.

Each Issuer will, in the event of any significant new factor, material mistake or inaccuracy relating to information included in this Base Prospectus which is capable of affecting the assessment of any Notes, prepare a supplement to this Base Prospectus or publish a new Base Prospectus for use in connection with any subsequent issue of Notes.

Unless otherwise stated, references to pages appearing in each of the cross-reference tables below are to those of each document incorporated by reference.

Cross Reference Table for NATIXIS:

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6

7

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Cross Reference Table for Natixis Structured Issuance:

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Cross reference table relating to previous Base Prospectuses:

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Appendix 3

DESCRIPTION OF THE ISSUERS

From the date of this Third Supplement, the section "DESCRIPTION OF THE ISSUERS" (appearing on pages 303 to 305 of the Base Prospectus) is amended as follows:

· sub-paragraph (a) "General" of paragraph 1. "Description of NATIXIS" (appearing on pages 303 to 304 of the Base Prospectus) is deleted in its entirety and replaced as follows:

"1. Description of NATIXIS(a) General

· Please refer to the relevant pages of the NATIXIS 2025 Universal Registration Document, which are incorporated by reference into this Base Prospectus, for a full description of NATIXIS (see Section "Documents Incorporated by Reference" of this Base Prospectus).

· On 4 November 2025, NATIXIS published the following press release:

"Groupe BPCE is positioned well above the prudential capital requirements applicable in 2026 as laid down by the European Central Bank

Paris, November 4, 2025

Groupe BPCE has received notification from the European Central Bank concerning the results of the Supervisory Review and Evaluation Process (SREP) conducted in 2025, stating the level of prudential capital requirements for 2025.

The Common Equity Tier 1 (CET1) requirement applicable to Groupe BPCE on a consolidated basis is unchanged at 10.59% as of January 1st, 2026, including:

· 1.69% with respect to the Pillar 2 requirement or P2R,

· 2.5% with respect to the capital conservation buffer,

· 1.0% with respect to the capital buffer for global systemically important banks (G-SIBs),

· 0.90% with respect to the countercyclical buffers.

The Total Capital requirement is also unchanged at 14.65% including 2.25% of P2R.

With ratios as of June 30th, 2025, of 16.3% for its CET1 ratio and 19.1% for its Total Capital ratio, Groupe BPCE is positioned well above the prudential capital requirements due to be applied as of January 1st, 2026.

The ECB also set Natixis' prudential capital requirements. Including 0.65% of countercyclical buffers on 1st January 2026, Natixis' CET1 ratio requirement is set at 8.84% on the same date including Pillar 2 requirement declining to 2.10%. With a fully loaded CET1 ratio of 11.7% as of June 30th, 2025, Natixis is also well above these regulatory requirements. Leverage ratio requirement will be set at 3.30% as of January 1st, 2026." "

· sub-paragraph (j) "Trend Information" of the paragraph 2. "Description of Natixis Structured Issuance" (appearing on pages 307 to 308 of the Base Prospectus) is deleted in its entirety and replaced as follows:  "(j) Trend Information

The year 2026 began with a radical geopolitical shift with the US military intervention in Venezuela. This military intervention appears to be a clear demonstration by the United States of its desire to establish the Western Hemisphere as a strategic sanctuary under its control, in contrast to the spheres of influence of China and Russia.

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Geopolitical uncertainty is thus far from dissipating, whether it concerns the war in Ukraine, the risk of China's annexation of Taiwan, Sino-Japanese tensions, or American expansionist ambitions regarding Greenland.

Moreover, the growing instability in the Middle East led to a US-Israeli military operation in Iran beginning on February 28. This operation has already had a significant impact, particularly on Brent crude oil and natural gas prices. One week after the conflict began, these stocks have risen by nearly $15 and more than 50%, respectively. Above all, the markets are reflecting a sharp rise in uncertainty, with stock indices falling (-5% for the Stoxx 600, -6% for the CAC 40, and -2% for the DJ). However, it is too early to speak of a potential supply shock, given the availability of alternative sources of production and current inventory levels. The economic impact will depend on the duration and intensity of the conflict. The macro-economic risk is very real, with the seeds of a stagflationary scenario that would combine rising prices with a slowdown in economic activity. For example, a $10 increase in oil prices would lead to 0.3 percentage points higher inflation and a 0.1 percentage point decline in GDP in France in the first year1 . The form the conflict might take and its possible outcome leave a wide range of possibilities. The latter depends, on the one hand, on the Iranian regime's ability to carry out significant strikes against the oil and gas infrastructure of countries bordering the Persian Gulf and to render the Strait of Hormuz impassable over the long term, and, on the other hand, the ability of Israel and the United States to quickly neutralize Iran's long-range strike capabilities and bring down the current regime. To date, Iran's strategy of regionalizing the conflict has not had the desired effects.

In contrast, trade tensions linked to rising protectionism have been gradually easing since the second half of 2025, leading to a normalization of supply chains. Global growth is expected to remain resilient, albeit slowing. According to the OECD, it is projected to decline from 3.2% in 2025 to 2.9% in 2026, largely due to the economic momentum that is already in place.

Provided that the conflict in the Middle East remains brief-lasting no more than a few weeks-the economic outlook for 2026 remains buoyed by the continuation of relatively favorable monetary conditions on both sides of the Atlantic. Slower than expected disinflation due to rising oil prices would be accompanied by robust economic activity. Another supporting factor is the widespread use of debt, particularly public debt, which should respond to increased defense efforts, as exemplified in Europe by the impact of Germany's recovery in defense and infrastructure investments.

More specifically, the United States is expected to see its growth rate slow (at +1.8%). Growth is also expected to slow in China (+4.8%, after +5.0%) and in the eurozone (+1.2%, after +1.5%), although the latter is driven to a greater extent by Germany (+1.3%, after +0.3%) than by Spain (+2.2%, after 2.9%) and, even more so, by Ireland. Emerging countries are expected to maintain the same momentum as in 2025 (+4.2%). US growth is expected to continue benefiting from surging investment in AI and support from strong consumption by the wealthiest households (a "K-shaped economy" scenario), despite a sharp slowdown in employment. China is expected to continue pursuing its economic trajectory as outlined in its 15th Five-Year Plan (2026-2030), which reaffirms the goals of strategic autonomy, strengthening the domestic market, and industrial modernization, particularly through innovation and AI. However, it would benefit slightly less from its growing desire to substitute imports and the hyper-competitiveness of its exports, due to the increasing difficulty of circumventing customs tariffs, even though these have risen less than announced. Excluding the specific performance of Ireland, activity in the eurozone is expected to improve in 2026, growing at a rate close to potential (+1.2%), in a context where inflation is expected to remain slightly below the 2.0% target. Growth should be further supported by the gradual revival of domestic demand and a slightly positive fiscal impulse, with the contribution of foreign trade remaining negative, as in 2025. In 2026, France should withstand, as in the previous year, continued political and budgetary uncertainty. GDP is expected to grow moderately by +1.0%, following +0.9% in 2025. Inflation, which has been brought under control by central banks without causing a recession, is expected to remain below the eurozone average throughout the year. It is expected to rise slightly by an annual average of +1.3% after +0.9% in 2025, due to the modest economic recovery and much more limited wage increases. Growth would benefit from global and European economic momentum, low inflation and energy prices, the impact of Germany's recovery in defense and infrastructure investment, and the delayed effects of monetary easing. Added to this would be the hoped-for reduction in the propensity to save. However, domestic demand would still be structurally hampered by the need to better control public accounts, which are increasingly constrained by the rising debt burden and the implementation of a European excessive deficit procedure, even if this adjustment appeared to be very incomplete. Indeed, the public deficit is expected to remain very high in 2026, at around 5.2% of GDP. In addition, a fiscal shock, the first signs of which began to appear in 2025, could undermine economic activity and employment.

1 Working Paper No. 2017/04 - "The Mésange Macro-econometric Model: Re-estimation and New Findings"

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However, the savings rate of French households is expected to decline very gradually, albeit from an extremely high level in 2025. After reaching 18.3%, it is expected to fall moderately to 18.1% in 2026. This trajectory is driven by fears of a foreseeable rise in unemployment and taxes. Indeed, the resurgence of specific concerns such as political uncertainty and worries about budgetary imbalances has partly replaced the feeling of declining purchasing power, particularly of financial assets, with the past surge in inflation. The recovery in household consumption would thus be limited, growing slightly faster than in 2025, in the absence of a significant increase in wage revenues. In particular, household purchasing power would increase slightly less than in 2025, due to the rebuilding of productivity and margins by companies and tax growth outpacing revenue growth. Similarly, the wait-and-see attitude linked to renewed uncertainty about public policy, the maintenance of high long-term interest rates, and weak demand would cause non-financial companies to slow down the expected rebound in investment in 2026, after it had virtually stagnated the previous year. Due to the carryover effect and slower growth in imports, foreign trade would continue to contribute to economic growth. The unemployment rate could reach 7.9%, after 7.7% in 2025, due to the mechanical recovery of productivity in the market sectors.

The global situation regarding prices and economic activity, both in many emerging economies and in most advanced countries, should perpetuate the implementation of monetary easing policies, except in Japan. The main reasons for this would be the less than expected inflationary impact of the trade war and concerns about economic activity stemming from the conflict in the Middle East. The Fed would choose to resolve the dilemma of its dual mandate (inflation and employment) by reducing its key rates by 75 basis points in increments of 25 basis points, in response to sluggish employment and rising unemployment. Considering the rise in prices resulting from customs tariffs to be temporary, it would seek to steer key rates toward a monetary neutrality floor, namely the 2.75%-3.00% range, despite a predictable spike in inflation around mid-2026, coinciding with the change in central bank president. Unless there is a sharp further depreciation of the dollar against the euro, the ECB is likely to keep its deposit facility rate anchored at 2.0%, which is the midpoint of the monetary neutrality range (1.75%-2.25%) and close to the inflation target.

The slope of the interest rate curve would continue to reform. Long-term rates are likely to show greater inertia on the downside, especially in France, due to an increase in the risk premium linked to rising public spending, the scale of debt, and the political difficulty of implementing structural reforms. Indeed, overall demand for public and private capital is expected to increase due to a period of high debt issuance ahead (increased competition among debtors) and, more specifically in Europe, an increased need for German financing. Thus, in the United States, 10-year rates could average 4.32% for the year, due to the Fed's continued monetary easing. Conversely, the 10-year OAT is expected to rise, due to the ECB's status quo and the risk of further deterioration in French public debt. The 10-year OAT would average around 3.73% per year, after 3.37% in 2025, with a spread of more than 76 basis points over the German Bund.

As always, these economic and financial forecasts are subject to uncertainty. As we begin 2026, and in light of recent events, they are primarily focused on developments in the conflict in the Near and Middle East. Based on the information available as of March 6, these projections are based on the assumption of a short-lived conflict- lasting no more than a few weeks-without escalation through a chain reaction of alliances. Under this scenario, inflation forecasts would be revised upward only slightly, and, as a result, growth forecasts would be revised downward very slightly."

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Appendix 4

GENERAL INFORMATION

From the date of this Third Supplement, the section "GENERAL INFORMATION" (appearing on pages 378 to 380 of the Base Prospectus) is amended as follows:

· the paragraph 3 entitled "Significant or material adverse change" (appearing on page 378 of the Base Prospectus) is deleted in its entirety and replaced as follows:

"3. Significant or material adverse change . In relation to NATIXIS:

There has been no significant change in the financial performance or financial position of NATIXIS and/or its consolidated subsidiaries taken as a whole since 31 December 2025.

There has been no material adverse change in the prospects of NATIXIS since 31 December 2025.

. In relation to Natixis Structured Issuance:

There has been no significant change in the financial performance or financial position of Natixis Structured Issuance since 31 December 2025.

There has been no material adverse change in the prospects of Natixis Structured Issuance since 31 December 2025."

· the paragraph 4 entitled "Litigation" (appearing on page 378 of the Base Prospectus) is deleted in its entirety and replaced as follows:

"4. Litigation

Except as set out in sections 3.2.10.1 "Legal and arbitration proceedings" and 3.2.10.2 "Other proceedings" on pages 162 to 165 of the NATIXIS 2025 Universal Registration Document incorporated by reference into this Base Prospectus, there are no governmental, legal or arbitration proceedings pending or threatened against NATIXIS or Natixis Structured Issuance during the twelve (12) months prior to the date hereof of which NATIXIS or Natixis Structured Issuance is aware, which may have or have had in such period a significant effect on the financial position or profitability of NATIXIS or Natixis Structured Issuance."

· the paragraph 8 entitled "Statutory Auditors" (appearing on page 374 of the Base Prospectus) is deleted in its entirety and replaced as follows:

"8. Statutory Auditors

The information in relation to the statutory auditors of NATIXIS is incorporated by reference into this Base Prospectus (see "DOCUMENTS INCORPORATED BY REFERENCE" section of the Base Prospectus).

PricewaterhouseCoopers Audit and Forvis Mazars SA (formerly Mazars) have audited and rendered an unqualified report on the consolidated financial statements of NATIXIS for each of the years ended 31 December 2024 and 31 December 2025.

Forvis Mazars (formerly Mazars Luxembourg), the statutory auditor of Natixis Structured Issuance, is registered as statutory auditor with the Luxembourg Institut des Réviseurs d'Entreprises.

Forvis Mazars has audited and rendered an unqualified audit report on the financial statements of Natixis Structured Issuance for each of the years ended 31 December 2024 and 31 December 2025."

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