His uncle, Pierre Cardinal Roger, Archbishop of Rouen, was elected pope in 1342 and took the name Clement VI.

Clement VI bestowed a number of benefices upon his nephew and in 1348, created the eighteen-year-old a cardinal deacon.

Gregory confirmed a treaty between Sicily and Naples at Villeneuve-lès-Avignon on 20 August 1372, which brought about a permanent settlement between the rival kingdoms, which were both papal fiefs.

[7] Efforts were also made to reform corrupt practices in the various monastic orders, such as collecting fees from persons visiting holy sites and the exhibiting of faux relics of saints.

The war ended with a peace treaty concluded at Tivoli in July 1378, negotiated with Pope Urban VI following the death of Gregory XI.

After 68 years of papal rule from France, Gregory XI moved the papacy back to its former seat of power of Rome in 1377.

Despite the protests of the French king and the majority of the cardinals, Gregory left Avignon on that day and made his way to Marseille, where he boarded a ship on 2 October.

On 13 January 1377, he left Corneto, landed at Ostia the next day, and from there sailed up the Tiber to the monastery of San Paolo.

[16] Subsequently, the Western Schism created by the selection of rival popes forced Europe into a dilemma of papal allegiance.