The Diocese of Tonga is a Latin Church ecclesiastical territory or diocese of the Catholic Church in Tonga. It was erected as part of the Vicariate Apostolic of Central Oceania in 1842, had subsequent name changes in 1937 and 1957 before being elevated to the Diocese of Tonga on June 21, 1966. Its cathedra is found in the Cathedral of the Immaculate Conception in the capital Nuku'alofa. It is immediately exempt to the Holy See and not part of an ecclesiastical province. Niue was part of the diocese until 1972, when it was transferred to the Diocese of Rarotonga.