Papal conclave, 1378

Coat of arms during the vacancy of the Holy See
Dates and location
7–9 April 1378 Old St. Peter's Basilica, Papal States
Key officials
Dean	Ange de Grimoard
Sub-Dean	Pietro Corsini
Protodeacon	Hugues de Saint-Martial
Elected Pope
Bartolomeo Prignano (Name taken: Urban VI)
← 1370 1389 →

The papal conclave from April 7 to 9, 1378 was the papal conclave which was the immediate cause of the Western Schism in the Catholic Church. The conclave was one of the shortest in the history of the Catholic Church. The conclave was also the first held in the Vatican and in Old St. Peter's Basilica (the elections and conclaves in Rome prior to the Avignon Papacy having been held mostly in the Basilica of St. John Lateran) since 1159.

Pope Gregory XI died on March 26, 1378 in Rome, having returned from Avignon to pursue his territorial interests in the Papal States during the War of the Eight Saints. Although the French cardinals constituted a majority of the College of Cardinals due to the preceding Avignon Papacy, they succumbed to the will of the Roman mob, which demanded the election of an Italian pontiff. They elected Bartolommeo Prignano, who took the name Pope Urban VI. This was the last time a non-cardinal was elected pope.

Before his death, Gregory XI substantially loosened the laws of the conclave: he instructed the cardinals to begin immediately after his death (rather than waiting the nine days prescribed by the Ordo Romanis) to prevent "factional coercion", he gave the cardinals permission to hold the conclave outside of Rome and move it as many times as necessary, and also seemingly suspended the two-thirds requirement, replacing it with "the greater part" (an ambiguous statement, in the original).

The cardinals were divided into three factions: the first constituting the four Italian cardinals (two Romans, one Florentine, and one Milanese), the second constituting the seven "Limoges" cardinals (referred to individually as "Limousins"), and the third constituting the five remaining French cardinals. The conclave was delayed one day because of a violent storm, and thereafter the seven Limoges cardinals wishing to leave Rome as Gregory XI had authorized them to were persuaded by the others that such an act would place the College in even more danger. It was midnight on the second day before the servants of the cardinals succeeded in clearing the Old Basilica of those not permitted to remain in the conclave.