NTT, Inc. (formerly known as Nippon Telegraph and Telephone Corporation) is a Japanese telecommunications holding 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. In 2023, the company was ranked 56th in the Forbes Global 2000. NTT was the world's largest company by market capitalization in the late 1980s, and remained among the world's top 10 largest companies by market capitalization until the burst of the Dot-com bubble in the early 2000s.

The company traces its origin to the national telegraph service established in 1868, which came under the purview of the Ministry of Communications in the 1880s as part of a postal, telegraph and telephone service. In 1952, the telegraph and telephone services were spun off as the government-owned Nippon Telegraph and Telephone Public Corporation. Under Prime Minister Yasuhiro Nakasone, the company was privatised in 1985 along with the Japan Tobacco and Salt Public Corporation and subsequently the Japanese National Railways two years later, adopting the previous name until July 2025. While NTT has been listed on the Tokyo Stock Exchange since 1987, the Japanese government still owns roughly one-third of NTT's shares, regulated by the NTT Law (Law Concerning Nippon Telegraph and Telephone Corporation, Etc.).

The company is incorporated pursuant to the NTT Law. The purpose of the company defined by the law is to own all the shares issued by NTT East and 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.