Marzio is a comune (municipality) located in the Province of Varese within the Lombardy region of northern Italy. It is situated approximately 60 kilometres northwest of Milan and about 13 kilometres north of the city of Varese. The municipality covers a total area of 1.98 square kilometres.
The territory of Marzio borders several neighboring municipalities, including Brusimpiano, Cadegliano-Viconago, Cuasso al Monte, Lavena Ponte Tresa, and Marchirolo. A notable geographical characteristic of the commune is that its territory is comprised within the Cinque Vette Park. The name "Marzio" may originate from the Latin name "Marcius" or potentially refer to the Italian word for "rotten."