SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 6-K

Report of Foreign Private Issuer

Pursuant to Rule 13a-16 or 15d-16

of the Securities Exchange Act of 1934

For the month of October 2025

Commission File Number 33-99720

ARAUCO AND CONSTITUTION PULP INC.

(Translation of registrant’s name into English)

El Golf 150

Fourteenth Floor

Santiago, Chile

(Address of principal executive offices)

Indicate by check mark whether the registrant files or will file annual reports under cover 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):  ¨

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):  ¨

Indicate by check mark whether the registrant by furnishing the information contained in this Form is also thereby furnishing the information to the Commission pursuant to Rule 12g3-2(b) under the Securities Exchange Act of 1934.

Yes  ¨                 No  x

If “Yes” is marked, indicate below the file number assigned to the registrant in connection with Rule 12g3-2(b): 82-  ¨

EXHIBITS

Exhibit	Description
99.1	Material Fact of Celulosa Arauco y Constitución S.A.

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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.

		Celulosa Arauco y Constitución S.A. (Registrant)
Date: October 24, 2025	By:	/s/ Cristián Infante Bilbao
	Name:	Cristián Infante Bilbao
	Title:	Chief Executive Officer

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