The river Ticino is the most important perennial left-bank tributary of the Po. It has given its name to the Swiss canton through which its upper portion flows.

The Po is the longest river in Italy. It flows eastward across northern Italy, starting from the Cottian Alps. The river's length is either 652 km (405 mi) or 682 km (424 mi), if the Maira, a right bank tributary, is included. The headwaters of the Po are a spring seeping from a stony hillside at Pian del Re, a flat place at the head of the Val Po under the northwest face of Monviso. The Po then extends along the 45th parallel north before ending at a delta projecting into the Adriatic Sea near Venice.