Origins in the Bronze Age
Late nineteenth-century finds of funerary urns show that the human presence in the area dates back at least to the Bronze Age, when people would have lived in settlements of pile dwellings raised above the rivers and marshes.
The Roman period
During the third century BCE the Romans subdued the Insubres, Gauls who had crossed the Alps and settled around Mediolanum (now Milan). A gallo-celtic tribe, who also seem to have been Insubres, then founded a village on the Lambro, of which the ruins of a bridge remain. Standing in a place where young people practised sports, the bridge was named ‘Arena’ and its remains can be seen near today’s Ponte dei Leoni (Lions Bridge).
During the Roman Empire the town was known as Modicia.
The Lombards
The Lombard invasion of Italy was an important event in Monza's history and the Lombard king Autari married Theodelinda, daughter of the Bavarian ruler Garibald I.
The new queen ordered the construction near the River Lambro of an oraculum, a sort of little church, that today is part of the basilica of Saint John. Paul the Deacon, an 8th century historian of the Lombards, tells us about this, writing: "[...] Theudelinda regina basilicam costruxerat, qui locus supra Mediolanum duodecim milibus abest, [...]" There is also an important legend that Theodelinda, asleep while her husband was hunting, saw in a dream a dove who told her : "Modo", Latin for "here", in order to say that she should build the oraculum in that place, and the queen answered "etiam", meaning "yes". So from the two words "modo" and "etiam", following the legend, would have derived "Modoetia", the medieval name of Monza.
Subsequent events
In the Middle Ages, the commune of Monza was sometimes independent, sometimes subject to Milan and the Visconti.
The first rail road built in North Italy was the Milan and Monza Rail Road opened for service on August 17th,1840.
On the evening of 29 July 1900 King Umberto I of Italy was assassinated in Monza by the anarchist Gaetano Bresci.