San Siro (Comasco: San Sir [ˌsãː ˈsiːr]) is a comune (municipality) in the Province of Como in the Italian region Lombardy, located on the west shore of Lake Como immediately north of Menaggio and south of Cremia.

The comune of San Siro incorporates the frazioni (municipal fractions) of Acquaseria, Camnasco, Carcente, Gallio, La Torre, Lancio Lucena, Marena, Mastena, Maso, Molvedo, Noledo, Pezzo, Rezzonico, Roncate, Santa Maria, San Martino, Soriano and Trecciano.

San Siro borders the following municipalities: Cremia, Menaggio, Plesio; and, on the other side of the lake in the Province of Lecco: Bellano, Dervio and Perledo.

There are other pieces of evidence in regards to the settlement's Roman period; such include two tablets inscribed in Latin (which are now held in Menaggio and Milan) and the remnants of a wall which dates to this era.

[3] Sights include the Rezzonico Castle, the 15th century church of Santa Maria and the Villa Gaeta, designed in 1920 by the studio of Gino Coppedè.