But does he really qualify for that role?
Let's examine the evidence, from the Gospel of John (John 20:24-29, New International Version):
Jesus Appears to Thomas
24 Now Thomas (called Didymus), one of the Twelve, was not with the disciples when Jesus came.
25 So the other disciples told him, “We have seen the Lord!”
25 So the other disciples told him, “We have seen the Lord!”
But he said to them, “Unless I see the nail marks in his hands and put my finger where the nails were, and put my hand into his side, I will not believe it.”
26 A week later his disciples were in the house again, and Thomas was with them. Though the doors were locked, Jesus came and stood among them and said, “Peace be with you!”
27 Then he said to Thomas, “Put your finger here; see my hands. Reach out your hand and put it into my side. Stop doubting and believe.”
28 Thomas said to him, “My Lord and my God!”
29 Then Jesus told him, “Because you have seen me, you have believed; blessed are those who have not seen and yet have believed.”
Thomas' skepticism is based on his statement that he won't believe Jesus is risen from the dead unless "I see the nail marks in His hands and put my finger where the nails were, and put my hand into His side."
And when Jesus appears to the disciples, He invites Thomas to do exactly that.
The problem for Christians who present this story to skeptics is that Thomas DID NOT FOLLOW THROUGH. Nowhere does it say, "And Thomas examined the nail marks in Jesus' hands, and put his fingers where the nails were, and carefully put his hand into the open wound on Jesus' side; and after doing all this, Thomas finally believed that this was indeed Jesus of Nazareth, the same Jesus who had died on the Cross just a short time ago."
No, Thomas just says, overwhelmed by the vision of Christ, "My Lord and my God!" So in spite of his skeptical-sounding words, he's just as eager as the rest of the disciples to believe that Jesus did, in fact, rise from the dead.
Why do I say the disciples were eager to believe in Jesus' resurrection? Well, for one thing, they'd behaved pretty badly during the hours leading up to Jesus' crucifixion. They'd fallen asleep when He practically begged them to stay awake and pray with Him.
Then when the guards showed up to arrest them, they all ran away instead of trying to help him.
Except Peter, His closest friend, who followed Him as far as the courtyard, but then denied Him three times and ran off crying his eyes out. (And John, who apparently ran away but came back later, standing with Jesus' mother, Mary, at the foot of the Cross; but didn't attempt any sort of rescue that we know of.)
I'm sure they felt pretty bad about themselves after the whole thing was over (as well they should have!). So the astonishing news that Jesus was alive - that He had had somehow survived that horrible, painful, ignominous death on the Cross, for which they were at least partly responsible - must have made them feel pretty cock-a-hoop.
And since they'd already witnessed the raising of Lazarus from the dead, there were grounds to believe this may in fact have actually happened.
So yes, Thomas was kind of skeptical, but no, he's not really the "Patron Saint of Skeptics". I'd say he's more the Patron Saint of People who Really Want to Be Convinced.