Innocent V (baptismal name Peter of Tarentaise, not to be confused with the earlier Peter of Tarentaise, 12th-century Cistercian archbishop) was born around 1225 in Champagny-en-Vanoise in Savoy to a Savoyard Catholic family.
He entered the Dominican Order around 1240 and studied at the University of Paris under St. Albert the Great — as the contemporary and fellow-student of St. Thomas Aquinas.
He became Master of Theology at the University of Paris around 1259 (the third Dominican master of theology at Paris after Sts. Albert and Thomas), holding the Dominican chair for multiple periods over the decades. He composed commentaries on the Sentences of Peter Lombard, Aristotelian commentaries, and theological treatises — one of the principal early-Dominican scholastics.
In 1272, Peter of Tarentaise was elected Archbishop of Lyon by Pope Gregory X. He served as one of the principal theological advisers at the Second Council of Lyon (May–July 1274) — the ecumenical council that attempted the reunion of the Latin-Catholic Western Church with the Greek-Byzantine Eastern Church (the reunion not lasting past the death of Byzantine Emperor Michael VIII Palaeologus in 1282).
At the Second Council of Lyon, Peter worked in collaboration with St. Thomas Aquinas (who died on the way to the Council on March 7, 1274 at the Abbey of Fossanova) and St. Bonaventure (who died during the Council on July 15, 1274) — the tragically brief overlap of the three principal Dominican-and-Franciscan theologians at the Council.
In 1273 Peter was created Cardinal-Bishop of Ostia. On the death of Pope Gregory X (January 10, 1276), Peter was elected Pope on January 21, 1276 at the conclave held at Arezzo — taking the papal name Innocent V and becoming the first Dominican Pope.
His pontificate lasted only five months (January 21 – June 22, 1276) — devoted to the implementation of the Second Council of Lyon's reunion-decrees, the reconciliation of the Guelph and Ghibelline factions in Italy, and the planning for the new Crusade to the Holy Land.
He died at Rome on June 22, 1276.

