Saltrio is a comune (municipality) in the Province of Varese in the Italian region Lombardy, located about 50 kilometres (31 mi) northwest of Milan and about 9 kilometres (6 mi) northeast of Varese, on the border with Switzerland. As of 31 December 2004, it had a population of 2,925 and an area of 3.5 square kilometres (1.4 sq mi).