Seveso (Italian pronunciation: [ˈsɛːvezo]; Lombard: Séves [ˈseːʋes]) is a town and comune in the Province of Monza and Brianza, in the Region of Lombardy.

Seveso lies on the national trunk road Statale dei Giovi, which connects Milan to Como and on the Milan-Meda motorway.

Seveso's origins date back to about the 3rd century BC, when certain areas around Brianza were used as military staging posts for the Roman conquest of Gaul.

Seveso made world headlines when, on 10 July 1976, storage vessels at the ICMESA chemical plant ruptured, releasing several kilograms of the dioxin TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) into the atmosphere.

Tens of thousands of farm animals and pets died or were later deliberately slaughtered, though it is believed that there was not a single human death directly attributable to the incident.