The Roman Catholic Diocese of Tianjin/Tíentsín (Latin:Latin: Tienzinen(sis), Chinese: 天津; pinyin: Tiānjīn) is a suffragan diocese in the ecclesiastical province of the Metropolitan Archbishop of Beijing in PR China.

Its cathedral episcopal see is Cathedral of St. Joseph (Laoxikai Church), in the city of Tianjin, which also houses the former cathedral Our Lady of Victory Church (Wanghailou Church) (圣母得勝堂（望海樓天主堂）).

Data from 1950 indicated there were 50,000 registered Roman Catholics in Tianjin, about 1.4% of the total 3,600,000 population.

Data from 2008 estimated 100,000 Catholics in Tianjin after years of persecution, of which 40,000 are officially registered and an estimated 60,000 are underground.

This article on a Roman Catholic diocese in Asia is a stub.