Paul was a native of Rome. He and his brother Stephen had been educated for the priesthood at the Lateran Palace. Stephen became pope in 752. After Stephen's death on 26 April 757, Paul prevailed over a faction that wanted to make Archdeacon Theophylact pope and was chosen to succeed his brother by the majority that wished a continuation of Stephen's policy.
Pontificate
Paul I's reign was dominated by relations with the Frankish and Lombard kings and with the Eastern Roman emperor. He adopted an independent tone in informing the imperial exarch in Ravenna of his election, but wrote to Pepin the Younger that the Frankish alliance should be maintained unimpaired. Paul was likely concerned of the danger posed by the Lombard kingDesiderius. The Lombards held the cities of Imola, Osimo, Bologna, and Ancona, which were claimed by the papacy, and in 758 seized upon the duchies of Spoleto and Benevento. On his return from suppressing a revolt in Benevento, Desiderius visited Rome and compelled Paul to write to Pepin asking him to concede all the Lombard claims. He promised to return Imola, but on condition that the pope should persuade Pepin to send back Lombard hostages held by the Franks. Paul agreed and sent a letter to Pepin. In a second secret letter, Paul advised Pepin of the agreement of Desiderius with the Byzantines for the conquest of Ravenna, and implored Pepin to come to the aid of the pope, and to force the Lombard king to yield the towns retained by him. Pepin found it advisable to maintain good relations with Desiderius, and Paul apparently accomplished little by his double-dealing. Later, however, Pepin gave the pope some support and acted as arbiter between the Roman and Lombard claims. In 765, papal privileges were restored in the duchies of Benevento and Tuscany and partially in Spoleto. Meanwhile, the alienation from Eastern Roman Empire grew greater. Several times, especially in 759, Paul feared that the emperor would send an armament against Rome. Paul lived in continual dread lest Eastern Roman ambitions turn the Frankish influence in favor of the Lombards. This was actually attempted, but Pepin held to his original foreign policy regarding Italy. Paul died in Rome on 28 June 767.