Lomazzo (Western Lombard: Lomazz [luˈmats]) is a town and comune in the province of Como, in the Italian region of Lombardy.

The ancient historical center of the town was founded on the top of a hill situated in the valley on the right bank of Lura.

For more than one thousand years, the central street of Lomazzo has been the political and religious border that cut the town in two parts, from south to the north.

Still in the 16th century the custom duties were collected at the passage of Lomazzo border, for the feudal rights granted to the Carcano family by the Spaniards, who at the time controlled the Duchy of Milan.

In 1282, Giovanni De Avvogadri, expelled by the Ghibellines from his bishopric in Come, excommunicated them from Lomazzo, starting the war between Como and Milan.