Châteaugiron (; ; Gallo: Chaujon) is a commune in the Ille-et-Vilaine department of Brittany in northwestern France. It extended on 1 January 2017 by merging with the former communes of Saint-Aubin-du-Pavail and Ossé.
Inhabitants of Châteaugiron are called Castelgironnais and Castelgironnaises in French.