Form 6-K NATIONAL GRID PLC For: Jun 09

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 June, 2026

Commission File Number: 001-14958

NATIONAL GRID plc

(Translation of registrant’s name into English)

1-3 Strand London WC2N 5EH, England

(Address of principal executive office)

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 ☒   Form 40-F ☐

EXPLANATORY NOTE

In connection with the issuance by National Grid plc of U.S.$750,000,000 aggregate principal amount of 5.405% Notes due 2036, National Grid plc is filing the following documents solely for incorporation into the Registration Statement on Form F-3 (File No. 333-281812):

Exhibit List

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.