According to the Vatican, the traditional “tomb of Paul” has been authenticated. Pope Benedict XVI announced that “tiny fragments of bone . . . belong to someone who lived in the first or second century.” “This seems to confirm the unanimous and undisputed tradition that these are the mortal remains of the Apostle St. Paul.”
The skeptical would note that a lot of people lived in the first and second centuries. However, these bones were within a tomb traditionally identified with Paul. I wouldn’t call that proof, but it seems to point in the direction of authenticity. At least, it is unlikely that somebody in the Middle Ages set this all up. CNN has a report.
Additionally, what is believed to be the earliest portrait of Paul was unveiled. The painting dates to the 4th century and shows the apostle with a thin face and a dark pointy beard. You can see for yourself here.