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SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Name of Issuer)

(Title of Class of Securities)

(CUSIP Number)

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

SCHEDULE 13D/A 0001429586 XXXXXXXX LIVE 12 Ordinary Shares, $1.00 par value per share 09/17/2025 false 0001190723 88031M109 Tenaris S.A. 26, BOULEVARD ROYAL 4TH FLOOR LUXEMBOURG N4 L-2449 Fernando J. Mantilla 352 27209600 26, Boulevard Royal, Ground Floor, Grand-Duchy of Luxembourg N4 L-2449 Y ROCCA & PARTNERS STICHTING ADMINISTRATIEKANTOOR AANDELEN SAN FAUSTIN OO N P7 0.00 713605187.00 0.00 713605187.00 713605187.00 N 68.5 HC Note to Row 4 (Source of funds): please refer to "Item 1 Comment" below. Note to Row 13 (Percent of class represented by amount in Row (11)): The percent of class figures set forth in this Amendment No. 12 are calculated based on 1,071,994,930 issued Ordinary Shares (as defined below), of which 29,499,198 were held by Tenaris S.A. as treasury stock as of September 12, 2025, as published on the website of Tenaris S.A. 0001429586 N SAN FAUSTIN S.A. OO N N4 0.00 713605187.00 0.00 713605187.00 713605187.00 N 68.5 CO Note to Row 4 (Source of funds): please refer to "Item 1 Comment" below. Note to Row 13 (Percent of class represented by amount in Row (11)): The percent of class figures set forth in this Amendment No. 12 are calculated based on 1,071,994,930 issued Ordinary Shares (as defined below), of which 29,499,198 were held by Tenaris S.A. as treasury stock as of September 12, 2025, as published on the website of Tenaris S.A. Y TECHINT HOLDINGS S.A R.L. OO N N4 713605187.00 0.00 713605187.00 0.00 713605187.00 N 68.5 CO Note to Row 4 (Source of funds): please refer to "Item 1 Comment" below. Note to Row 13 (Percent of class represented by amount in Row (11)): The percent of class figures set forth in this Amendment No. 12 are calculated based on 1,071,994,930 issued Ordinary Shares (as defined below), of which 29,499,198 were held by Tenaris S.A. as treasury stock as of September 12, 2025, as published on the website of Tenaris S.A. Ordinary Shares, $1.00 par value per share Tenaris S.A. 26, BOULEVARD ROYAL 4TH FLOOR LUXEMBOURG N4 L-2449 This Amendment No. 12 amends and supplements the Schedule 13D originally filed on February 14, 2011 (this "Amendment No. 12"), as further amended by Amendments No. 1, No. 2, No. 3, No. 4, No. 5, No. 6, No. 7, No. 8, No. 9, No. 10 and No. 11, on behalf of RP STAK, SAN FAUSTIN and TECHINT HOLDINGS (each as defined under Item 2 below) (collectively, the "Reporting Persons"), relating to the Ordinary Shares, par value $1 per share of Tenaris S.A. (the "Ordinary Shares"). This Amendment No. 12 reflects (i) the authorization given by SAN FAUSTIN's board of directors to TECHINT HOLDINGS to sell a number of its Ordinary Shares, provided that TECHINT HOLDINGS' ownership stake in Tenaris S.A. should not fall below 67 percent of the total outstanding Ordinary Shares (see Item 4 below) and (ii) an increase by 0.91% of the percent of class represented by the Ordinary Shares held by such Reporting Persons, from 67.54% to 68.45%, as reported on Rows 13 of the cover pages of this Schedule 13D, as a result of repurchases of Ordinary Shares made by Tenaris S.A. in the open market in the period from July 7, 2025 to September 12, 2025, under Tenaris S.A.'s 2025-2026 share buyback program publicly announced on May 27, 2025. Except as specifically provided herein, this Amendment No. 12 does not modify any of the information previously reported on the Schedule 13D and its amendments. This Schedule 13D is being jointly filed by each of the Reporting Persons pursuant to Rule 13d-1(k). ROCCA & PARTNERS STICHTING ADMINISTRATIEKANTOOR AANDELEN SAN FAUSTIN ("RP STAK"). Fascinatio Boulevard 764, 2909 VA Capelle aan den IJssel, The Netherlands. SAN FAUSTIN S.A. ("SAN FAUSTIN") 26, Boulevard Royal, Ground Floor, L-2449 Luxembourg. TECHINT HOLDINGS S.A R.L. ("TECHINT HOLDINGS") 26, Boulevard Royal, Ground Floor, L-2449 Luxembourg. RP STAK is a private foundation (stichting) organized under the laws of The Netherlands. No person or group of persons controls RP STAK SAN FAUSTIN is a societe anonyme (public limited liability company) organized under the laws of the Grand-Duchy of Luxembourg. RP STAK continues to control SAN FAUSTIN (i.e. it continues to have the ability to influence matters affecting, or submitted to a vote of the shareholders of SAN FAUSTIN, including the election of directors and the approval of certain corporate transactions and other matters concerning SAN FAUSTIN's policies). TECHINT HOLDINGS is a societe a responsabilite limitee (private limited liability company) organized under the laws of the Grand-Duchy of Luxembourg. All of the shares of TECHINT HOLDINGS are held by SAN FAUSTIN. The name, residence or business address, present principal occupation or employment (and the name, principal business and address of any corporation or other organization in which such employment is conducted) and citizenship of each voting committee member, executive officer or director, as applicable, of each Reporting Person are set forth in Exhibit 99.1 to the Amendment No. 11 to the Schedule 13D of Tenaris S.A., filed on July 8, 2025, and is incorporated into this Item 2 by reference. During the last five years, none of the Reporting Persons, nor, to the knowledge of the Reporting Persons, none of the persons listed on Exhibit 99.1 to the Amendment No. 11 to the Schedule 13D of Tenaris S.A., filed on July 8, 2025, has been convicted in a criminal proceeding (excluding traffic violations or similar misdemeanors). Information with respect to each of the Reporting Persons is given solely by such Reporting Person, and no Reporting Person assumes responsibility for the accuracy or completeness of information given by another Reporting Person. During the last five years, none of the Reporting Persons, nor, to the knowledge of the Reporting Persons, none of the persons listed on Exhibit 99.1 to the Amendment No. 11 to the Schedule 13D of Tenaris S.A., filed on July 8, 2025, has been a party to a civil proceeding of a judicial or administrative body of competent jurisdiction and as a result of such proceeding was or is subject to a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to federal or state securities laws or finding any violation with respect to such laws. Information with respect to each of the Reporting Persons is given solely by such Reporting Person, and no Reporting Person assumes responsibility for the accuracy or completeness of information given by another Reporting Person. The last disclosure paragraph of the response set forth in Item 4 of the Schedule 13D originally filed on February 14, 2011, is hereby deleted in its entirety and replaced with the following: For portfolio-management purposes and in response to Tenaris S.A.'s ongoing share repurchase program causing SAN FAUSTIN's beneficial ownership interest in Tenaris S.A. to passively increase, on September 17, 2025, the board of directors of SAN FAUSTIN authorized TECHINT HOLDINGS to sell a number of its Ordinary Shares, provided that TECHINT HOLDINGS' ownership stake in Tenaris S.A. should not fall below 67 percent of the total outstanding Ordinary Shares. The precise timing, amount and manner of any such sales will depend upon market conditions and other factors, and there is no assurance that any sales will be completed or the timing thereof. Although the Reporting Persons do not currently intend to purchase Ordinary Shares or to reduce their beneficial ownership below 67 percent of the total outstanding Ordinary Shares, they may from time to time, depending on market conditions and other factors, purchase or sell additional Ordinary Shares. Except as described in this Schedule 13D, the Reporting Persons do not have any present plans or proposals that relate to or would result in any of the actions described in subparagraphs (a) through (j) of Item 4 of Schedule 13D. RP STAK. See items (7) through (11) and (13) on page 2 SAN FAUSTIN. See items (7) through (11) and (13) on page 3 TECHINT HOLDINGS. See items (7) through (11) and (13) on page 4 RP STAK. See items (7) through (11) and (13) on page 2 SAN FAUSTIN. See items (7) through (11) and (13) on page 3 TECHINT HOLDINGS. See items (7) through (11) and (13) on page 4 During the last 60 days, there have been no transactions in Ordinary Shares effected by the Reporting Persons or, to the best of the Reporting Person's knowledge, any of the persons listed on Exhibit 99.1 to the Amendment No. 11 to the Schedule 13D of Tenaris S.A., filed on July 8, 2025. N/A N/A A Power of Attorney of ROCCA & PARTNERS STICHTING ADMINISTRATIEKANTOOR AANDELEN SAN FAUSTIN dated October 31st, 2023.* B Power of Attorney of SAN FAUSTIN S.A., dated September 28, 2023.* C Power of Attorney of TECHINT HOLDINGS S.a r.l., dated September 28, 2023.* *Previously filed as an exhibit to the Amendment No. 5 to the Schedule 13D of Tenaris S.A. filed on November 3, 2023 and incorporated by reference in this Amendment No. 12. ROCCA & PARTNERS STICHTING ADMINISTRATIEKANTOOR AANDELEN SAN FAUSTIN ROCCA & PARTNERS STICHTING ADMINISTRATIEKANTOOR AANDELEN SAN FAUSTIN /s/ Fernando J. Mantilla / Attorney-in-fact 09/19/2025 SAN FAUSTIN S.A. SAN FAUSTIN S.A. /s/ Fernando J. Mantilla / Attorney-in-fact 09/19/2025 TECHINT HOLDINGS S.A R.L. TECHINT HOLDINGS S.A R.L. /s/ Fernando J. Mantilla / Attorney-in-fact 09/19/2025 Pursuant to Rule 13d-1(k)(1), the undersigned joins in the filing of this Amendment No. 12 on his own behalf and on behalf of SAN FAUSTIN S.A. and TECHINT HOLDINGS S.A R.L. Pursuant to Rule 13d-1(k)(1), the undersigned joins in the filing of this Amendment No. 12 on his own behalf and on behalf of ROCCA & PARTNERS STICHTING ADMINISTRATIEKANTOOR AANDELEN SAN FAUSTIN and TECHINT HOLDINGS S.A R.L. Pursuant to Rule 13d-1(k)(1), the undersigned joins in the filing of this Amendment No. 12 on his own behalf and on behalf of ROCCA & PARTNERS STICHTING ADMINISTRATIEKANTOOR AANDELEN SAN FAUSTIN and SAN FAUSTIN S.A.