Tortona (anc. Dertona), a town and episcopal see of Piedmont, Italy, in the province of Alessandria, from which it is 14 m. E. by rail, on the right bank of the Scrivia, at the northern foot of the Apennines, 394 ft. above sea-level. Pop. (1901), r t,308 (town); 17,419 (commune). Tortona is on the main line from Milan to Genoa; from it a main line runs to Alessandria, a branch to Castelnuovo Scrivia, and a steam tramway to Sale. Its fortifications were destroyed by the French after Marengo (1799); the ramparts are now turned into shady promenades. The cathedral, erected by Philip II., contains a remarkably fine Roman sarcophagus of the Christian period. Silk-weaving, tanning and hat-making are the chief industries; and there is some trade in wine and grain.
Dertona, which may have become a Roman colony as early as the 2nd century B.C. and certainly did so under Augustus, is spoken of by Strabo as one of the most important towns of Liguria. It stood at the point of divergence of the Via Postumia (see LIGURIA) and the Via Aemilia, while a branch road ran hence to Pollentia. A number of ancient inscriptions and other objects have been found here. In the middle ages Tortona was zealously attached to the Guelphs, on which account it was twice laid waste by Frederick Barbarossa, in 1155 and 1163. (T. As.)