Casalzuigno (Casàl Sciuìgn in lombard) is a comune (municipality) in the Province of Varese in the Italian region Lombardy, located about 60 kilometres (37 mi) northwest of Milan and about 14 kilometres (9 mi) northwest of Varese.

Arcumeggia, a frazione of the municipality of Casalzuigno has, on the external walls of the houses, some paintings, performed with the technique of the fresco, by Italian artists of the 20th century.

Casalzuigno borders the following municipalities: Azzio, Brenta, Castelveccana, Cuveglio, Cuvio, Duno, Porto Valtravaglia.

Casalzuigno is located in Valcuvia, a region inhabited since prehistoric times by Ligurians, probably coming from the settlements of Lake Varese.

The settlement of the Ligurians in Valcuvia gave rise to the so-called civilization of the Man of Valcuvia confirmed by the discovery of a prehistoric ax in the hamlet of Arcumeggia, part of the current municipality of Casalzuigno.