The date of Adrian's birth is unknown, but is believed to be about the year 700. He was the son of Theodore, a Roman nobleman, but little else is known of his youth. He served under Popes Paul I and Stephen IV. He ascended to the papal [[cathedra]] on [[February 1]], 772 with the support of the Frankish party in Rome. Adrian's policies thereafter were determined generally by the Frankish alliance rather than by his relations with emperors of Constantinople.
Shortly after having become the Pope of Rome, the Byzantine territories of the Exarchate of Ravenna and the Duchy of Rome were invaded by the king of the Lombards, Desiderius. Answering Adrian's call for help, Charlemagne attacked the Lombard capital, Pavia. After taking Pavia, Charlemagne defeated Desiderius and took the title of King of the Lombards himself. Under the protection of the Frankish king, Adrian was able to add to the Duchy of Rome the territories and cities along the Adriatic Sea that came under his temporal control as the Papal States. With these successes, Pope Adrian celebrated by striking the earliest papal coin.