A traditional tale attributes the foundation of the bishopric of Apt to a saint named Auspicus, whom Pope Clement I sent and who died a martyr in 102; but the first documented evidence of its existence is in the acts of the Synod of Arles of 314, at which Apt was represented by a priest and an exorcist. Early 5th-century bishop Saint Castor of Apt is mentioned in contemporary liturgical documents and in a 419 letter of Pope Boniface I. The diocese appears in documents of the same century as a suffragan of Aix. As a result of the concordat of 15 July 1801 between Pope Pius VII and Napoleon Bonaparte, the territory of the diocese was incorporated by the bull "Qui Christi Domini" of 29 November of the same year mainly into the archdiocese of Avignon, with some parishes going instead to the diocese of Digne. No longer a residential bishopric, Apta (as it is called in Latin) is today listed by the Catholic Church as a titular see.