d. 1091

German cleric and scholar who in about 1090 wrote a treatise on astronomy and built what would become a famous model of the planetary system. Abbot of Hirsau from 1069, Wilhelm supported the vigorous reforms of Pope Gregory VII and instituted reforms at his own monastery, where he promoted liberal studies. His works include Constitutiones Hirsaugienses, Dialogi de musica, and De astronomia.