Po, river in Italy, that country’s longest, called Padus in Latin Padus. The Po rises in the Monte Viso group of the Cottian Alps on Italy’s western frontier and empties into the Adriatic Sea in the east after a course of 405 miles (652 km). Its drainage basin covers 27,062 square miles (70,091 square km), forming Italy’s widest and most fertile plain.

Tributaries: Tanaro.

Source: Encyclopaedia Britannica.