Saint Matthias (Μαθθίας in Greek, מַתִּתְיָהוּ Hebrew) was chosen to replace Judas Iscariot following Judas's betrayal and Christ's Passion.
Saint Peter gathered 120 disciples together and proposed that two men would be nominated to replace Judas. Once the group had chose Joseph called Barsabas and Saint Matthias they prayed together and cast lots - Saint Matthias had the lot fall on him, and so was chosen to be the replacement for Judas.
Greek tradition holds that Saint Matthias travelled throughout Cappadocia spreading the faith and lived mostly on the port Issus. Nicephorus recorded that Saint Matthias preached first in Judaea, then Aethiopia. It was there in Aethiopia (modern day Georgia) that Saint Matthias was stoned to death and martyred. In the 11th century his feast was included in the Roman Calendar for February 25th (sixth day in the Calends of March) but was transferred during the 1969 revision for May 14th. This May 14th date was chosen so that the feast would not fall within Lent but would still be celebrated close to the Solemnity of the Feast of the Ascension as Saint Matthias was chosen as an apostle prior to the Ascension of Christ.