Apostle (Greek apostolos, “one sent forth”), messenger, especially one of the 12 disciples whom Jesus Christ sent forth to preach the gospel and to act in his name. Jesus may have selected 12 apostles because of the 12 tribes in Israel, thus signifying that the Christian community is God's Israel (see Gal. 6:16), which inherits the privileges of ancient Israel. The Twelve were Peter, Andrew, James the Great, John, Philip, Bartholomew, Thomas, Matthew, James the Less, Thaddaeus, Simon the Canaanite, and Judas Iscariot. Matthias was chosen in place of Judas (see Acts 1:26). In the early church the title apostle was extended to others who spread the Christian message, such as Paul, Barnabas, and Timothy.

The founder of the Christian church in a country is usually spoken of as the apostle of that country; thus, Gregory of Armenia is the apostle of Armenia. Other apostles so identified include St. Boniface, of Germany; St. Augustine, of England; St. Patrick, of Ireland; St. Columba, of Scotland; St. Cuthbert, of Northumbria; and St. Denis, of France.