the disciple who, according to the biblical Acts of the Apostles 1:21–26, was chosen to replace Judas Iscariot after Judas betrayed Jesus.

Jesus' choice of 12 Apostles points to a consciousness of a symbolic mission—originally there were 12 tribes of Israel—that the community maintained after the Crucifixion. Acts reveals that Matthias accompanied Jesus and the Apostles from the time of the Lord's Baptism to his Ascension and that, when it became time to replace Judas, the Apostles cast lots between Matthias and another candidate, St. Joseph Barsabbas. St. Jerome and the early Christian writers Clement of Alexandria and Eusebius of Caesarea attest that Matthias was among the 72 disciples paired off and dispatched by Jesus. Soon after his election, Matthias received the Holy Spirit with the other Apostles (Acts 2:1–4). He is not mentioned again in the New Testament.

It is generally believed that Matthias ministered in Judaea and then carried out missions to foreign places. Greek tradition states that he Christianized Cappadocia, a mountainous district now in central Turkey, later journeying to the region about the Caspian Sea, where he was martyred by crucifixion and, according to other legends, chopped apart. His symbol, related to his alleged martyrdom, is either a cross or a halberd. St. Helena, mother of the Roman emperor Constantine the Great, reputedly transported Matthias' relics from Jerusalem to Rome.