Castano Primo (Italian pronunciation: [ˈkastano ˈpriːmo]; Milanese: Càstan) is a city and comune in Province of Milan, in the Italian region Lombardy, located about 35 kilometres (22 miles) northwest of Milan.

Castano Primo borders the following municipalities: Lonate Pozzolo, Vanzaghello, Magnago, Nosate, Buscate, Cameri, Turbigo, Robecchetto con Induno, Cuggiono. It received the honorary title of city with a presidential decree on October 11, 1984.

Castano was initially a Roman village that subsequently came under the Burgaria of Parabiago. It was converted to a military fortress by the Counts of Biandrate, passing eventually to the House of Visconti. During internal struggles within the House of Visconti, Castano was pillaged.