The (Roman Catholic) Diocese of Nakhon Ratchasima (Dioecesis Nakhonratchasimaensis, Thai: สังฆมณฑลนครราชสีมา) is located in the north-east of Thailand.

It is a suffragan diocese of the Archdiocese of Thare and Nonseng.

The diocese covers an area of 41,148 km², covering 3 provinces of Thailand - Buriram, Chaiyaphum and Nakhon Ratchasima; as of 2023, of the 5.2 million citizens of the three provinces, 5,721 were members of the Catholic Church.

The diocese was created on March 22, 1965, when the Vicariate Apostolic of Ubon was split.

December 18, 1965 the Vicariate Apostolic of Nakhorn-Rajasima was elevated to a diocese.