Sebastian was a Gallo-Roman officer in the Praetorian Guard under Diocletian. As a captain of the imperial palace guard, he secretly visited Christian prisoners, brought them sacraments, and used his position to protect them. When his Christianity was discovered, Diocletian ordered him bound to a stake and shot to death by archers.
He was pierced 'as full of arrows as a hedgehog of quills,' left for dead. The widow Irene of Rome, coming to take his body for burial, found him still alive and nursed him back to health. Restored, Sebastian sought out the emperor on the steps of the imperial palace and rebuked him for the persecution. Diocletian had him beaten to death with clubs; his body was cast into the Cloaca Maxima. A pious woman recovered it and buried him in the catacombs on the Appian Way.
His basilica on the Appian Way is one of the seven pilgrim churches of Rome. Together with St. Roch he is invoked particularly against plague — by the 14th-century black death his cult had become universal across Europe. His iconography — the beautiful young man pierced with arrows — became one of the most painted subjects of the Italian Renaissance.