St. Matthias is recognized as one of the twelve apostles of Jesus Christ. He was chosen to replace Judas Iscariot after Judas betrayed Jesus and subsequently died. The selection of Matthias is described in the New Testament, specifically in the Book of Acts, where the remaining apostles cast lots to determine who would take Judas's place. Traditionally, St. Matthias is celebrated on February 24th in the Christian calendar. He is often depicted in art holding a book or a sword, symbolizing his role as a witness to the teachings of Jesus and his martyrdom. His feast day is observed by various Christian denominations, including the Catholic Church and the Eastern Orthodox Church.