The Catechism in Questions & Answers

435. What were the names of the first twelve Apostles?

The names of the first twelve Apostles were: Simon who was called Peter, Andrew, James, John, Philip, Bartholomew, Thomas, Matthew, James the son of Alpheus, Lebbaeus, whose surname was Thaddaeus, Simon the Canaanite, and Judas Iscariot (cf. Matthew 10: 2-4). These Apostles are called the “twelve” even after the betrayal of Judas Iscariot.