The Diocese of Wanxian, also known as Diocese of Wanzhou, is a Latin Catholic diocese located in Wanzhou District, Chongqing in the ecclesiastical province of Chongqing, in the easternmost part of western China. It was established on August 2, 1929 as the Apostolic Vicariate of Wanhsien for the Mission of Sichuan (Szechwan).