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 August 2023

Commission File Number: 001-38638

NIO Inc.

(Registrant’s Name)

Building 20, 56 Antuo Road

Jiading District, Shanghai 201804

People’s Republic of China

(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 o

EXHIBIT INDEX

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.

Date: August 16, 2023

Exhibit 99.1

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

Under our weighted voting rights structure,our share capital comprises Class A ordinary shares and Class C ordinary shares. Each Class A ordinary share entitles the holder to exerciseone vote, and each Class C ordinary share entitles the holder to exercise eight votes, respectively, on any resolution tabled at our generalmeetings, except as may otherwise be required by law or by the Rules Governing the Listing of Securities on The Stock Exchange of HongKong Limited or provided for in our memorandum and articles of association. Shareholders and prospective investors should be aware ofthe potential risks of investing in a company with a weighted voting rights structure. Our American depositary shares, each representingone of our Class A ordinary shares, are listed on the New York Stock Exchange in the United States under the symbol NIO.

NIO Inc.

(A company controlled throughweighted voting rights and incorporated in the Cayman Islands with limited liability)

(Stock Code: 9866)

DATE OF BOARD MEETING

Our board of directors will hold a board meeting on Tuesday, August 29, 2023 (Beijing/Hong Kong Time) for the purposes of, among other things, approving our unaudited results and announcement for the three months and six months ended June 30, 2023 (“Q2 2023 Results”). The Company will publish its Q2 2023 Results on Tuesday, August 29, 2023 (Beijing/Hong Kong Time) on the website of The Stock Exchange of Hong Kong Limited at www.hkexnews.hk and the Company’s website at ir.nio.com.

The Company’s management will host an earnings conference call at 8:00 p.m. Beijing/Hong Kong Time on August 29, 2023 (8:00 a.m. U.S. Eastern Time on August 29, 2023). A live and archived webcast of the conference call will be available on the Company’s investor relations website at https://ir.nio.com/news-events/events.

For participants who wish to join the conference using dial-in numbers, please register in advance using the link provided below and dial in 10 minutes prior to the call. Dial-in numbers, passcode and unique access PIN would be provided upon registering.

https://s1.c-conf.com/diamondpass/10033043-ysg6dg.html

Hong Kong, August 16, 2023

As of the date of this announcement, the boardof directors of the Company comprises Mr. Bin Li as the chairman, Mr. Lihong Qin, Mr. James Gordon Mitchell as the directors, and Mr.Hai Wu, Mr. Denny Ting Bun Lee and Ms. Yu Long as the independent directors.