Tortona (Italian: [torˈtoːna]; Piedmontese: Torton-a [tʊrˈtʊŋa], locally [tʊrˈtɔŋa]; Latin: Dertona) is a comune of Piemonte, in the Province of Alessandria, Italy.

[3] Known in ancient times as Dertona, the city was probably the oldest colony under Roman rule in the westernmost section of the Valley of the Po, on the road leading from Genua (Genoa) to Placentia (Piacenza).

Velleius mentions it among those founded under the Republic, it appears to have been recolonised under Augustus; some inscriptions therefore give it the title of Julia Dertona.

[4] The assassin of Caesar, Brutus, encamped at Dertona on his march in pursuit of Mark Antony, after the Battle of Mutina,[5] and it was one of the places where a body of troops was usually stationed during the later ages of the empire.

One of the rulers in this period was Facino Cane, who in the unsettled affairs of Lombardy had assembled a string of lordships and great wealth which he bequeathed to his wife, Beatrice, and arranged with his friends that a marriage should be effected between her and Filippo Maria Visconti.

[10] Then following the vicissitudes of the War of the Polish Succession, the city was occupied by the King of Sardinia, and "count of Tortona" was added to the titles of the House of Savoy.