Tenaris S.A. — Proxy Solicitation & Information Statement 2026

Apr 17, 2026

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Tenaris S.A. Société Anonyme 26, Boulevard Royal, 4th Floor. L-2449 Luxembourg RCS Luxembourg B 85 203

NOTICE OF THE ANNUAL GENERAL MEETING OF SHAREHOLDERS AND OF AN EXTRAORDINARY GENERAL MEETING OF SHAREHOLDERS

to be held in Luxembourg on 12th May 2026

Notice is hereby given to holders of ordinary shares of Tenaris S.A. (the “Company”) that the Annual General Meeting of Shareholders of the Company will be held on 12th May 2026, at 10:00 (Central European Time) and that an Extraordinary General Meeting of Shareholders of the Company will be held immediately after the adjournment of the Annual General Meeting of Shareholders. Both meetings (the “Meetings”) will be held at the Company’s registered office located at 26, Boulevard Royal, 4th Floor, L-2449 Luxembourg, Grand-Duchy of Luxembourg.

At the Annual General Meeting of Shareholders, shareholders will vote on the items listed below under the heading “Agenda for the Annual General Meeting of Shareholders”. At the Extraordinary General Meeting of Shareholders, shareholders will vote on the items listed below under the heading “Agenda for the Extraordinary General Meeting of Shareholders”.

Agenda for the Annual General Meeting of Shareholders

1. Consideration of the Company’s consolidated annual management report for the year ended 31st December 2025, which includes the following information and certifications required by applicable law: (i) consolidated financial and non-financial information (or sustainability statement) for the year ended 31st December 2025; (ii) related management certifications on the Company’s consolidated financial statements as of and for the year ended 31st December 2025, and on the annual accounts as at 31st December 2025; and (iii) external auditors’ reports on such consolidated financial statements, annual accounts and non-financial information (or sustainability statement).

2. Approval of the Company’s consolidated financial statements as of and for the year ended 31st December 2025.

3. Approval of the Company’s annual accounts as at 31st December 2025.

4. Allocation of results and approval of dividend payment for the year ended 31st December 2025.

5. Discharge of the members of the Board of Directors for the exercise of their mandate throughout the year ended 31st December 2025.

6. Election of the members of the Board of Directors.

7. Approval of the compensation payable to the members of the Board of Directors for the year ending 31st December 2026.

8. Approval of the Company’s compensation report for the year ended 31st December 2025.

9. Appointment of the Company’s statutory auditors for the fiscal year ending 31st December 2026, and approval of their fees.

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1. Authorization to the Company, or any subsidiary, to purchase, acquire or receive securities of the Company, in accordance with Article 430-15 of the Luxembourg law of 10 August 1915 and with applicable laws and regulations.

2. Authorization to the Board of Directors to cause the distribution of all shareholder communications, including its shareholder meeting and proxy materials and annual reports to shareholders, by such electronic means as is permitted by any applicable laws or regulations.

Agenda for the Extraordinary General Meeting of Shareholders

1. Approval of (a) the cancellation of 62,355,174 ordinary shares held in treasury, acquired by the Company throughout the third share buyback program, which ran from 9th June 2025 to 3rd March 2026, and (b) the consequential reduction of the issued share capital of the Company by an amount of US$62,355,174 so as to bring it from its current amount of US$1,071,994,930 to US$1,009,639,756, represented by 1,009,639,756 ordinary shares with a nominal value of US$1.00 per share.

2. The amendment of article 5 “Share Capital” of the Company’s articles of association to reflect the resolutions on item 1 of the agenda.

Meetings: vote requirements

Resolutions at the Annual General Meeting of Shareholders will be passed by the simple majority of the votes validly cast, irrespective of the number of shares present or represented.

The Extraordinary General Meeting of Shareholders may not validly deliberate on the proposed amendment of the Company’s articles of association unless at least half of the issued share capital is represented, unless otherwise provided for by applicable law. If the required quorum is not reached at the first Extraordinary General Meeting of Shareholders, a second Extraordinary General Meeting of Shareholders may be convened in accordance with the Company’s articles of association and applicable law and such second Extraordinary General Meeting of Shareholders shall validly deliberate regardless of the number of shares represented. Resolutions at the Extraordinary General Meeting of Shareholders shall be adopted by a two-third majority of the votes validly cast, unless otherwise provided for by applicable law.

Holders of Shares: procedures for attending and voting at the Meetings

In accordance with the Luxembourg Law of 24 May 2011 on the exercise of certain rights of shareholders in general meetings of listed companies, as amended (the “Shareholders’ Rights Law”), the right to attend, speak and vote at the Meetings is restricted to those shareholders who are holders of shares of the Company on 28th April 2026 at 24:00 (midnight), Central European Time (the “Shareholders’ Record Time”).

Shareholders will only be entitled to attend and/or to vote (personally or by proxy) at one or both Meetings in respect of those shares of the Company which each shareholder duly evidences to hold at the Shareholders’ Record Time. Any changes to a shareholder’s holding of shares after the Shareholders’ Record Time shall be disregarded for purposes of determining the right of such shareholder to attend and/or to vote (personally or by proxy) at the Meetings.

Set out below are instructions on how to attend and/or vote (personally or by proxy) at one or both Meetings.

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If you are a holder of shares of the Company on the Shareholders’ Record Time and you wish to attend and/or vote (personally or by proxy) at the Meetings, you must complete and return to the Company:

i. the Intention to Participate Form, if you wish to attend the Meetings; and/or ii. the AGMS/EGMS Proxy Form, if you wish to vote by proxy at the Meetings.

Shareholders wishing to attend one or both Meetings must complete and return to the Company the Intention to Participate Form. The Intention to Participate Form must be received by the Company, properly completed and signed, ON OR BEFORE 28th APRIL 2026 AT 24:00 (MIDNIGHT), CENTRAL EUROPEAN TIME (i.e., THE SHAREHOLDERS’ RECORD TIME). Shareholders who have timely submitted the Intention to Participate Form may elect either to (i) attend one or both Meetings and vote in person (in which case the shareholder is not required to submit the AGMS/EGMS Proxy Form), or (ii) have a proxy holder attend one or both Meetings in person and vote by proxy, in which case shareholders must also submit (in addition to the Intention to Participate Form) the AGMS/EGMS Proxy Form as soon as possible and, in any event, must be received by the Company ON OR BEFORE 4th MAY 2026 AT 24:00 (MIDNIGHT), CENTRAL EUROPEAN TIME. Please note that in the event that the Company does not receive the Intention to Participate Form and, if applicable, the AGMS/EGMS Proxy Form, properly completed and signed, by the dates indicated above, such shareholder will not be able to participate or vote (neither in person nor by proxy) at the Meetings. Shareholders and proxy holders attending the Meetings in person will be required to identify themselves at the Meetings with a valid official identification document (e.g., identity card or passport). In the event of shares registered to the name of a corporation or any other legal entity, individuals representing such corporation or legal entity who wish to attend the Meetings in person and vote at the Meetings on behalf of such legal entity, must submit –in addition to the Intention to Participate Form and the AGMS/EGMS Proxy Form, as indicated above– a legal evidence of their authority to represent the shareholder at the Meetings (such as a general or special power-of-attorney or any other proper document) issued by the such legal entity (the “Power of Attorney”). A copy of the Power of Attorney must be received by the Company on or before 4th MAY 2026 AT 24:00 (MIDNIGHT), CENTRAL EUROPEAN TIME.

Shareholders who do not wish to attend the Meetings but nonetheless wish to vote by proxy at one or both Meetings must only complete and return to the Company the AGMS/EGMS Proxy Form (and do not need to submit the Intention to Participate Form nor a Power of Attorney), which must be received by the Company ON OR BEFORE 28th APRIL 2026 AT 24:00 (MIDNIGHT), CENTRAL EUROPEAN TIME (i.e., THE SHAREHOLDERS’ RECORD TIME). Please note that in the event that the Company does not receive the AGMS/EGMS Proxy Form, properly completed and signed, by the date indicated above, such shareholder will not be able to vote (neither in person nor by proxy) at any Meeting.

In addition, any shareholder wishing to attend and/or vote (personally or by proxy) at one or both Meetings is required to provide reasonably satisfactory evidence to the Company (prior to the Meetings) as to the number of shares of the Company held by such shareholder on the Shareholders’ Record Time. Such evidence of shareholding must be provided by means of a certificate issued by each shareholder’s bank or stockbroker, which must include at least the shareholder’s name, the shareholder’s registered office/address, the number of shares held by the shareholder on the Shareholders’ Record Time, the stock exchange on which the shareholder’s shares trade and signature of the relevant shareholder’s bank or stockbroker (the “Certificate of Shareholding”). The Certificate of Shareholding must be delivered to the Company as soon as possible and in any event must be received by the Company ON OR BEFORE 4th MAY 2026 AT 24:00 (MIDNIGHT), CENTRAL EUROPEAN TIME.

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In compliance with the Shareholders’ Rights Law and other applicable laws and regulations, this convening notice (which contains the agendas for the Meetings and the procedures for attending and/or voting at the Meetings), the total number of shares of the Company and voting rights as of the date of this notice, the Shareholder Meeting Brochure and Proxy Statement (which contains reports on each item of the agendas for the Meetings and draft resolutions proposed to be adopted at the Meetings), the Company’s 2025 consolidated annual report, which includes (i) the consolidated management report containing the consolidated financial and non-financial information (or sustainability statement) together with the required management certifications and external auditors’ reports, and (ii) the Company’s consolidated financial statements as of and for the year ended 31st December 2025, and the Company’s annual accounts as at 31st December 2025, the 2025 Compensation Report, the proposed amendments to the Company’s articles of association, the Intention to Participate Form, the AGMS/EGMS Proxy Form and the model Certificate of Shareholding, required to be submitted to the Company for purposes of participating and/or voting at the Meetings, are available to shareholders as of the date of this notice, and may be obtained free of charge from the Company’s website at ir.tenaris.com/corporate-governance/annual-general-meeting or at the Company’s registered office in Luxembourg. In addition, shareholders registered in the Company’s registry may obtain electronic copies of these documents free of charge by sending an electronic message to the following electronic addresses: investors@tenaris.com and fgbettiol@tenaris.com.

The Intention to Participate Form and, if applicable, the Power of Attorney (if you wish to attend the Meetings), the AGMS/EGMS Proxy Form (if you wish to be represented and vote by proxy at the Meetings) and the Certificate of Shareholding must be received by the Company, properly completed and signed, by the dates indicated above, at any of the following postal addresses, or by electronic message to the following electronic addresses: investors@tenaris.com and fgbettiol@tenaris.com.

Luxembourg: 26, Boulevard Royal, 4th Floor, L-2449 Luxembourg Attn: Ana Maria Grandes Muñoz

Italy: c/o Dalmine S.p.A. Piazza Caduti 6 luglio 1944 n. 1 24044 Dalmine (BG) Attn: Marco Maria Domenico Tajana and/or Francesco Giuseppe Bettiol

Mexico: c/o Tubos de Acero de México, S.A. Campos Elíseos 400-Piso 17 Col. Chapultepec Polanco 11560 Ciudad de México Attn: Ulises Martínez Martínez and/or Carol B. Clemente Bejarano

In the case of shares held through fungible securities accounts in Mexico, the Certificate of Shareholding must be issued by S.D. Indeval Institución para el Depósito de Valores S.A. de C.V. (Paseo de la Reforma #255, 3er. piso Col. Cuauhtémoc, Mexico City) in accordance with applicable regulation.

The AGMS/EGMS Proxy Form will only be valid if it includes the shareholder’s name, registered office/address and signature and, in the event of shares owned by a corporation or any other legal entity, the name, registered office/address and signature of the individual (s) representing such corporation or other legal entity. INCOMPLETE OR ERRONEOUS

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AGMS/EGMS PROXY FORMS OR AGMS/EGMS PROXY FORMS THAT ARE NOT TIMELY DELIVERED OR DO NOT SATISFY THE REQUIRED FORMALITIES WILL BE DISCARDED AND THE UNDERLYING SHARES WILL NOT BE VOTED AT THE MEETINGS.

A shareholder’s proxy holder shall enjoy the same rights to speak and ask questions at the Meetings as those afforded to the respective shareholder. Pursuant to the Shareholders’ Rights Law, irrespective of the number of shares held, a shareholder may appoint only one proxy holder to represent such shareholder at the Meetings, except that:

(i) if a shareholder holds shares of the Company through more than one securities account, such shareholder may appoint one proxy holder for each securities account; and

(ii) a shareholder acting professionally for the account of a natural person or legal entity may appoint such natural person or legal entity, or any other third party designated by them, as proxy holder.

A person acting as shareholder’s proxy holder may represent one or more shareholders. In the event a person represents more than one shareholder, such proxy holder may vote the shares of the represented shareholders differently, in accordance with the instructions given to such proxy holder by each shareholder such person represents.

Each share is indivisible for purposes of attending and voting at the Meetings. Co-owners of shares, beneficiaries and bare-owners of shares, and pledgors and pledges of pledged shares must be represented by one single person at the Meetings.

In accordance with the Shareholders’ Rights Law, shareholders holding, individually or collectively, at least five per cent (5%) of the issued share capital of the Company have the right to (a) include items on the agenda for the Meetings; and (b) propose draft resolutions for the items included or to be included on the agenda for the Meetings. To exercise such rights, shareholders holding, individually or collectively, at least five per cent (5%) of the issued share capital of the Company, must submit a written request to the Company on or before 20th April 2026, to any of the postal addresses of the Company indicated above, or by sending an electronic message to the following electronic addresses: investors@tenaris.com and fgbettiol@tenaris.com. The request must be accompanied by a justification or a draft resolution proposed to be adopted in the Meetings and must include the postal or electronic address at which the Company can acknowledge receipt of such request. Requests which are not timely delivered or do not satisfy the required formalities will be discarded and the proposals included in such requests shall not be included in the agenda for the Meetings.

In accordance with the Shareholders’ Rights Law, shareholders (or their proxy holders) will have the right to ask questions at the Meetings on the items of the agendas for the Meetings. The right to ask questions, and the Company’s duty to answer any such questions, are subject to the procedures adopted by the Company to ensure the proper identification of shareholders (and their proxy holders), the good order of the Meetings, as well as the protection of confidentiality of the Company’s business and the safeguarding of the Company’s corporate interests.

Holders of ADRs: procedures for voting at the Meetings

Holders of American Depositary Receipts (“ADRs”) as of 28th April 2026 (the “ADR Holders’ Record Date”) are entitled to instruct DEUTSCHE BANK TRUST COMPANY AMERICAS, as Depositary (the “Depositary”), as to the exercise of the voting rights in respect of the Company’s shares underlying such holder’s ADRs. Only those ADR holders of record as of the

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ADR Holders’ Record Date will be entitled to provide the Depositary with voting instructions.

Proxy materials will be available to ADR holders as of the date of this notice on the Company’s website at ir.tenaris.com/corporate-governance/annual-general-meeting. Voting instructions and voting cards will be sent to ADR holders by the Depositary. Eligible ADR holders who wish to give voting instructions in respect of the shares underlying ADRs must follow the instructions and meet the deadlines set forth in such voting instructions and voting cards.

In accordance with the Luxembourg law of 11 January 2008 on transparency obligations for issuers of securities, as amended, each shareholder of the Company must notify the Company and the Luxembourg Commission de Surveillance du Secteur Financier (CSSF) on an ongoing basis whenever the proportion of the Company’s voting rights held or controlled by such shareholder (or shareholders acting in concert) reaches, exceeds or falls below any of the following thresholds: 5%, 10%, 15%, 20%, 25%, 33 1/3%, 50% and 66 2/3%. Any such notification shall be made as indicated in the Company’s website at tenaris.com/en/sustainability/governance-and-ethics/ and in accordance with CSSF regulations. Failure to make such notification will cause the suspension of the exercise of voting rights relating to the shares exceeding the proportion that should have been notified.

On 10th April 2026, the Company had a total issued share capital of US$ 1,071,994,930, represented by 1,071,994,930 shares, each share carrying one vote (which includes 62,355,174 shares held in treasury (with their voting rights suspended) that have been repurchased by the Company under its third share buyback program and are pending cancellation).

Cecilia Bilesio Secretary of the Board of Directors

10th April 2026 Luxembourg