He was reportedly born in Narbonne to a Milanese mother married to a Roman official. Allegedly a member of the praetorian guard at Rome, because of his loyalty he served as a pesonal guard to the emperors Diocletian and Maximian.

As a Christian, he suffered martyrdom in Rome at the beginning of the persecution of Diocletian. His tomb in the place named Ad Catacumbas on the Via Appia has been venerated by the faithful from the earliest times.

The martyrdom of St. Sebastian, about whom little is known, has been a subject for countless artists to portray the male body. St. Sebastian was killed by multiple arrow shots, an image of suffering and redemption which provided the basis for his cult. Georges Eekhoud seems to have been the first to make the connection between the art of St. Sebastian and homoeroticism.