theologian principally remembered for his leadership of the losing side in the crucial eucharistic controversy of the 11th century.

Having studied under the celebrated Fulbert at Chartres, Berengar returned to Tours after 1029 and became canon of its cathedral and head of the School of Saint-Martin, which rivaled Bec under Lanfranc, who was later to be his opponent. Berengar befriended Geoffrey, Count of Anjou, and Eusebius Bruno, later bishop of Angers. About 1040 he was appointed archdeacon of Angers.

Shortly thereafter, Berengar, who always exhibited great independence of thought, began to teach ideas contrary to prevailing beliefs. Most notably, he rejected the then-current view of transubstantiation credited to the 9th-century abbot of Corbie, St. Paschasius Radbertus, who professed that the bread and wine, after consecration in the mass, became the real body and blood of Christ. Berengar favoured the interpretation formulated in De corpore et sanguine Domini (“Concerning the Body and Blood of the Lord”) by Ratramnus, a monk of Corbie, to whom the elements became the body and blood of Christ in a symbolic sense. Berengar's restatement of these views aroused severe opposition. He boldly wrote (c. 1050) to Lanfranc against his condemning Ratramnus. The letter arrived in Lanfranc's absence and, after being read by several persons, finally reached him at Rome. Pope Leo IX excommunicated Berengar at the Easter Synod of 1050 and ordered him to the Council of Vercelli (1050). Berengar reluctantly obeyed. He went to Paris to get permission from the French king Henry I, his nominal abbot, to attend the synod. He was imprisoned by Henry and condemned at Vercelli in absentia.

On his release from prison, Berengar took refuge with his protector, Geoffrey, and Henry ordered a synod at Paris to judge Berengar and his supporter Eusebius. The synod condemned them both (1051). In 1054 the powerful papal legate Cardinal Hildebrand came to France to preside at the Synod of Tours. To preserve peace, a compromise was reached under which Berengar signed a vague eucharistic statement. In 1059 he was summoned to Rome for another council, at which he was refused a hearing and was asked to sign an extreme statement repugnant to his ideas. After this, Geoffrey died, and Eusebius began to draw away from Berengar. Berengar nevertheless published a treatise (c. 1069) against the Roman council of 1059, which was answered by Hugo of Langres and by Lanfranc, with a rejoinder by Berengar.

Berengar's position was steadily worsening, and the rigorous pattern of examination, condemnation, and recantation was repeated at the nearly violent Council of Poitiers (1076), the Roman synods of 1078 and 1079, and a trial at Bordeaux in 1080. Thereafter Berengar was silent. He retired to ascetic solitude in the priory of Saint-Cosme.

Berengar's eucharistic doctrine is expressed in his De sacra coena (“On the Holy Supper”), written in reply to Lanfranc. More than any of his contemporaries, Berengar applied to theological development the method of dialectic. He based his argument on belief that Paschasius' view was contrary to the Scriptures, the Church Fathers, and reason.