Also called Didymus ('twin'). When Jesus announced he was returning to Judea where people had tried to stone him, Thomas said 'Let us also go, that we may die with him.' After the resurrection he was absent when Jesus appeared to the disciples and famously declared he would not believe unless he could put his fingers in Jesus' wounds. A week later Jesus appeared again and Thomas responded 'My Lord and my God!'
Philip, and Bartholomew; Thomas, and Matthew the publican; James the son of Alphaeus, and Lebbaeus, whose surname was Thaddaeus;Matthew 10:3, KJV
John 11:16
Then said Thomas, which is called Didymus, unto his fellowdisciples, Let us also go, that we may die with him.John 11:16, KJV
John 14:5
Thomas saith unto him, Lord, we know not whither thou goest; and how can we know the way?John 14:5, KJV
John 20:25
The other disciples therefore said unto him, We have seen the Lord. But he said unto them, Except I shall see in his hands the print of the nails, and put my finger into the print of the nails, and thrust my hand into his side, I will not believe.John 20:25, KJV
John 20:28
And Thomas answered and said unto him, My Lord and my God.John 20:28, KJV
Acts 1:13
And when they were come in, they went up into an upper room, where abode both Peter, and James, and John, and Andrew, Philip, and Thomas, Bartholomew, and Matthew, James the son of Alphaeus, and Simon Zelotes, and Judas the brother of James.Acts 1:13, KJV
See how Thomas connects to every other figure in Scripture.