Pope Caius or Pope Gaius was pope from 283 until his death in 296. He was the son of Gaius, or, according to St. Susanna of Concordius, a relative of the emperor Diocletian, and became pope on December 17, 283. His tomb, with the original epitaph, was discovered in the catacombs of Calixtus and in it the ring with which he used to seal his letters (see Arringhi, Roma subterr., 1. iv. c. xlviii. p. 426).
His feast is on April 22, together with Pope Soter. Saint Caius is portrayed in art wearing the Papal Tiara with Saint Nereus. He is venerated in Dalmatia and Venice.