Four Saints in Three Acts is an opera by American composer Virgil Thomson with a libretto by Gertrude Stein. Written in 1927-8, it contains about 20 saints, and is in at least four acts. It was ground breaking for form, content, and its all-black cast, with singers directed by Eva Jessye, a prominent black choral director, and supported by her choir.

Thomson suggested the topic, and the libretto as delivered can be read in Stein's collected works. The opera features two 16th-century Spanish saints—the former mercenary Ignatius of Loyola and the mystic Teresa of Avila—as well as their colleagues, real and imagined: St. Plan, St. Settlement, St. Plot, St. Chavez, etc. Thomson decided to divide St. Teresa's role between two singers, "St. Teresa I" and "St. Teresa II", and added the master and mistress of ceremonies (Compère and Commère—literally, the "godparents") to sing Stein's stage directions.