St. Innocent I reigned as pope from 401 to 417.

He is known for his condemnation of the heresy of Pelagianism, which denied the effects of Original Sin and misconstrued free will, and the excommunication of its proponent, Pelagius. Through this action, which confirmed the decision of the synod of bishops in Carthage, St. Innocent I emphasized papal supremacy.

His pontificate coincides with the siege of Rome by Alaric the Visigoth (408-410), during which he had to leave the city and was involved in peace efforts conducted on Ravenna.