Thaddeus (Greek Thaddaios) is one of the Twelve Apostles of Jesus referred to in Matthew and Mark. In Luke 6:16 and Acts 1:13 his name is replaced with "Judas the son of James", indicating that Thaddeus might be a family name. The manuscript of the King James Version identifies "Lebbaeus, whose surname was Thaddeus" in Matthew 10:3. This ambiguity about Thaddeus's identity has led to speculations that he may be one of the seventy Jesus sent out after His Ascension rather than one of the Twelve. In the Catholic tradition, however, he is considered synonymous with Saint Jude, often referred to as Saint Jude Thaddeus.
St. Thaddeus is credited, along with St. Bartholomew as having introduced Christianity to Armenia.