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 August 2021

Commission File Number 001-13314

Huaneng Power International, Inc.

(Translation of registrant’s name into English)

Huaneng Power International, Inc.

Huaneng Building,

6 Fuxingmennei Street,

Xicheng District,

Beijing, 100031 PRC

(Address of principal executive office)

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): ¨

This Form 6-K consists of:

An announcement regarding issue of mid-term notes of Huaneng Power International, Inc.(the "Registrant"), made by the Registrant on August 20, 2021.

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.

Hong Kong Exchanges and Clearing Limited and The Stock Exchange of Hong Kong Limited take no responsibility for the contents of this announcement, make no representation as to its accuracy or completeness and expressly disclaim any liability whatsoever for any loss howsoever arising from or in reliance upon the whole or any part of the contents of this announcement.

OVERSEAS REGULATORY ANNOUNCEMENT ISSUE OF MID-TERM NOTES

This announcement is made pursuant to Rule 13.10B of the Rules Governing the Listing of Securities on The Stock Exchange of Hong Kong Limited (the “Listing Rules”).

As resolved at the 2020 annual general meeting of Huaneng Power International, Inc. (the “Company”) held on 22 June 2021, the Company has been given a mandate to issue domestic and/or overseas debt financing instruments after relevant regulatory department approval (including but not limited to domestic debt financing instruments like corporate bonds, enterprise bonds, mid-term notes in the interbank bond markets in the domestic market, and overseas debt financing instruments like offshore RMB-denominated bonds, overseas USD-denominated bonds and bonds denominated in other foreign currencies in the overseas market) (in either one or multiple tranches on rolling basis) with a principal amount of up to RMB80 billion or equivalent within or outside the People’s Republic of China within the period from approval obtained at 2020 annual general meeting to the conclusion of the 2021 annual general meeting.

The Company has recently completed the issue of the first tranche of the Company’s mid-term notes (sustainably-linked) for 2021 (the “Mid-Term Notes”). The issuing amount of the Mid-Term Notes was RMB2 billion for a term of 3 years. The unit face value is RMB100 and the issuing interest rate is 2.99%.

Bank of Ningbo Co., Ltd. and Shanghai Pudong Development Bank Co., Ltd. acted as the lead underwriters to form the underwriting syndicate for the Mid-Term Notes, which were placed through book-building and issued in the domestic interbank market. All proceeds from the Mid-Term Notes will be used to supplement the working capital of the headquarters of the Company, adjust debts structure and repay bank loans and the debt due.

The relevant documents in respect of the Mid-Term Notes are posted on China Money and Shanghai Clearing House at websites of www.chinamoney.com.cn and www.shclearing.com, respectively.

The Mid-Term Notes do not constitute any transaction under Chapter 14 and Chapter 14A of the Listing Rules.

As at the date of this notice, the directors of the Company are:

Beijing, the PRC

20 August 2021