6-K

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 6-K

REPORT OF FOREIGN PRIVATE ISSUER

PURSUANT TO RULE 13a-16 OR 15d-16

UNDER THE SECURITIES EXCHANGE ACT OF 1934

For the Month of July 2024

Commission File Number: 001-38097

ARGENX SE

(Translation of registrant’s name into English)

Laarderhoogtweg 251101 EB Amsterdam, the Netherlands

(Address of principal executive offices)

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

EXPLANATORY NOTE

On July 16, 2024, argenx SE (the “Company”) issued an investor presentation, a copy of which is attached hereto as Exhibit 99.1, and is incorporated by reference herein.

The information contained in this Current Reporton Form 6-K, including Exhibit 99.1, shall be deemed to be incorporated by reference into the Company’s Registration Statementson Forms F-3 (File No. 333-258251) and S-8 (File Nos. 333-225375, 333-258253, and 333-274721), and to be part thereof fromthe date on which this Current Report on Form 6-K is filed, to the extent not superseded by documents or reports subsequently filedor furnished.

SIGNATURES

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.

Exhibit 99.1