The Diocese of Thanh Hóa (Latin: Dioecesis de Thanh Hoa) is a Roman Catholic diocese of Vietnam.

The bishop since 2018 is Joseph Nguyễn Đức Cường.

Of the three million persons living in its area about 3% are Roman Catholics.

Saint Anne Cathedral in Thanh Hoa city has been assigned as the Cathedral of the diocese.

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