Casorate Sempione is a comune (municipality) in the Province of Varese in the Italian region Lombardy, located northwest of Milan and about southwest of Varese. As of 31 December 2004, it had a population of 5,334 and an area of .
Casorate Sempione borders the following municipalities: Arsago Seprio, Cardano al Campo, Gallarate, Somma Lombardo.
In Casorate it is still celebrated the party of San Tito, that has been celebrated for the first time in 1926, in order to remember the XV centenary of the death of the martyr. The party is revived every ten years for an amount of time of a couple of weeks. The last edition has taken place in September 2016.
Casorate Sempione is twinned with: