Castello Cabiaglio is a comune (municipality) in the Province of Varese in the Italian region Lombardy, located about northwest of Milan. As of 31 December 2004, it had a population of 548 and an area of .
Castello Cabiaglio borders the following municipalities: Barasso, Brinzio, Comerio, Cuveglio, Cuvio, Luvinate, Rancio Valcuvia, Varese.