(d. 1090/1095 in Aversa) was a monk in La-Croix-St-Leufroy who studied under Lanfranc of Bec. He declined appointments to bishoprics in England and Rouen, but agreed to become bishop in Aversa in 1088. As an opponent of Berengar of Tours, he did preliminary work on the doctrine of transsubstantiation with the concept of the mutatio substantiva.
PL 149, 1427–1512
G. Macy, The Theologies of the Eucharist in the Early Scholastic Period, 1984
M. Dell'Omo, “Ricerche biografiche su Guitmondo,” Ben. 40, 1993, 9–34.