Pope Pelagius I (died 3 March 561) was the bishop of Rome from 16 April 556 to his death on 3 March 561.
Pelagius accompanied Pope Agapetus I to Constantinople and was appointed apocrisiarius. As such, Pelagius acquired great influence with Emperor Justinian I. He returned to Rome in 543. While before his ordination he opposed Justinian's efforts to condemn the "Three Chapters" in order to reconcile theological factions in the Church, afterwards Pelagius adopted Justinian's position.
Pelagius I's pontificate was undermined by rumors that he might have somehow been complicit in the death of Vigilius, and suspicion that his conceding to Justinian indicated a support for monophysitism. To overcome this he worked to maintain public order in Rome, and correct abuses among the clergy. He also labored on behalf of the poor and the victims of famine and war. In response to a request from the garrison commander at Civitavecchia, Pelagius directed Bishop Lawrence of that town, to provide chaplains for the army. He is credited with the construction of the Santi Apostoli, Rome, built to celebrate the complete victory of Narses over the Ostrogoths.
Pelagius I served for five years, and upon his death on 3 March 561 was buried in Old St. Peter's Basilica.