Busto Arsizio is a comune (municipality) in the south-easternmost part of the province of Varese, in the Italian region of Lombardy, 35 kilometres (22 mi) north of Milan. The economy of Busto Arsizio is mainly based on industry and commerce. It is the fifth municipality in the region by population and the first in the province.

The province of Varese is a province in the Lombardy region of Italy. Its capital is the city of Varese, but its largest city is Busto Arsizio. The headquarters of AgustaWestland, the company merged into Leonardo since 2016 and the world's largest producer of helicopters, is based in Samarate, a comune (municipality) of the province. As of 2015, it has a population of 889,410 inhabitants over an area of 1,198.11 square kilometres (462.59 sq mi). The province contains 139 comuni.