Guillaume \gu(i)-llau-me\ as a boy's name is pronounced gee-OHM. It is of Old German origin, and the meaning of Guillaume is "will helmet, protection". French variant of William. Guillermo (gui-YARE-mo) is a Latin form. French poet Guillaume Apollinaire.
Guillaume has 6 variant forms: Gillermo, Guglielmo, Guilherme, Guillermo, Gwillyn and Gwilym.