The term underground church (Chinese: ?; pinyin: ) is used to refer to Chinese Catholic churches in the People's Republic of China which have chosen not to associate with the state-sanctioned Chinese Patriotic Catholic Association, they are also called loyal church (Chinese: ?; pinyin: ). Underground churches came into existence in the 1950s, after the communist party's establishment of the People's Republic of China, due to the severing of ties between Chinese Catholics and the Holy See.
The description of an "underground church" reflects language that was made popular during the Cold War, when these churches came about. Underground churches are also sometimes referred to as "Vatican loyalists" because they have attempted to remain loyal to the Pope and the Holy See. There is no established organization structure of underground churches, though they tend to be clustered around a number of Vatican-ordained bishops. However, underground churches would in 1989 form the Bishops Conference of Mainland China (Chinese: ?; pinyin: ) as separate from the state-sanctioned Bishops Conference of Catholic Church in China (Chinese: ; pinyin: ), which was established in 1980.
Chinese Catholics associated with underground churches are often seen in contrast with the Chinese Catholics associated with the Chinese Patriotic Catholic Association, often termed "open churches" (Chinese: ?; pinyin: ; lit. 'above ground church'), which are officially independent of the Holy See.