Ambrogio Damiano Achille Ratti, pope 1922–1939. Signed the Lateran Treaty (1929) that created Vatican City and ended the Roman Question. He coined the term "Catholic Action" for lay involvement in Church affairs. He condemned both Nazism (Mit brennender Sorge, 1937) and Communism (Divini Redemptoris, 1937). His concordat with Hitler (1933) proved controversial.
- Lived: 1857 CE – 1939 CE
- Nationality: Italian
- Roles: Pope, Cleric
