The Nippon Telegraph and Telephone Corporation, commonly known as NTT, is a Japanese telecommunications company headquartered in Tokyo, Japan. Ranked 55th in Fortune Global 500, NTT is the fourth largest telecommunications company in the world in terms of revenue, as well as the third largest publicly traded company in Japan after Toyota and Sony, as of June 2022.

The company is incorporated pursuant to the NTT Law (Law Concerning Nippon Telegraph and Telephone Corporation, Etc.). The purpose of the company defined by the law is to own all the shares issued by Nippon Telegraph and Telephone East Corporation (NTT East) and Nippon Telegraph and Telephone West Corporation (NTT West) and to ensure proper and stable provision of telecommunications services all over Japan including remote rural areas by these companies as well as to conduct research relating to the telecommunications technologies that will form the foundation for telecommunications.

On 1 July 2019, NTT Corporation launched NTT Ltd., an $11 billion de facto holding company business consisting of 28 brands from across NTT Security, NTT Communications and Dimension Data.

While NTT is listed on the Tokyo Stock Exchange and the OTC Markets Group's Pink (and formerly in the New York Stock Exchange under the ticker code "NTT" and in the London Stock Exchange under the ticker code "NPN"), the Japanese government still owns roughly one-third of NTT's shares, regulated by the NTT Law.