Ferno is a comune in the Province of Varese in the Italian region Lombardy, located about 40 km northwest of Milan and about 35 km south of Varese. As of 31 December 2017, it had a population of 6,858 and an area of 8.5 km2. The municipality of Ferno contains the frazione San Macario. Ferno borders the following municipalities: Lonate Pozzolo, Samarate, Somma Lombardo, Vizzola Ticino. It is served by Ferno-Lonate Pozzolo railway station.