Pope Caius (died 22 April 296),[1] also called Gaius, was the bishop of Rome from 17 December 283 to his death in 296.

[1] As pope, Caius decreed that before someone could assume the position of bishop, he must first be porter, lector, exorcist, acolyte, subdeacon, deacon, and priest.

[5][4] Pope Caius would go into hiding due to increased persecution of the church, alongside Saints Polycarp, Sebastian, Tranquillinus, Tiburtius, Nicostratus and Zoe, in the house of Castulus, a Christian officer employed at the Imperial Palace.

[7] Caius would be found praying with Tiburtius shortly after the conversion and baptism of Tiburtius' children and the pair was brought to the local Praefectus, a man named Fabian, who ordered the construction of a great bonfire, and ordered the two to either throw frankincense into it to appease the Roman gods, or to cast themselves into it.

[2] Caius' tomb, with the original epitaph, was discovered in the catacomb of Callixtus and in it the ring with which he used to seal his letters (see Arringhi, Roma subterr., 1. iv.

However, it was demolished in 1880 to make room for the Ministry of War, on the Via XX Settembre, and his relics were transferred to the chapel of the Barberini family.