For the massacre of a similar name, see Saint Bartholomew's Day Massacre
Bartholomew (Saint Bartholomew in Catholic and Orthodox traditions) was one of Jesus's twelve Apostles. Historians suggest that he was the same person as Nathaniel, as mentioned in John 1:45-51 and 21:2. He was one of the disciples to whom Jesus appeared at the Sea of Tiberias after His resurrection. He was also a witness of the Ascension. 
Like most Apostles, Bartholomew was martyred, probably at Albanopolis in Armenia. He was probably flayed alive and crucified by the order of Astyages. The likely reason was that Bartholomew converted Astyages' brother Polymius, King of Armenia, to Christianity. Because of this legend Bartholomew is often shown in art as flayed and holding in his hand his own skin. Michelangelo's Last Judgment displays Bartholomew in this manner.
Feastday: August 24 (Roman); 11 June (Orthodox).
Prayer to Saint Bartholomew the Apostle
O Glorious Saint Bartholomew, Jesus called you a person without guile and you saw in this word a sign that he was the Son of God and King of Israel. Obtain for us the grace to be ever guileless and innocent as doves. At the same time, help us to have your gift of faith to see the Divine hand in the events of daily life. May we discern the signs of the times that lead to Jesus on earth and will eventually unite us to him forever in heaven. Amen.