The Po (Latin: Padus and Eridanus, Italian: Po Italian pronunciation: [ˈpɔ], ancient Ligurian: Bodincus or Bodencus, Greek: Πάδος and Ἠριδανός) is a river that flows either 652 km (405 mi) or 682 km (424 mi) – considering the length of the Maira, a right bank tributary – eastward across northern Italy, from 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 (in the Cottian Alps) through a delta projecting into the Adriatic Sea near Venice. It has a drainage area of 74,000 km² in all, 70,000 in Italy, of which 41,000 is in montane environments and 29,000 on the plain. The Po is the longest river in Italy; at its widest point its width is 503 m (1,650 ft). The Po extends along the 45th parallel north.

The river flows through many important Italian cities, including Turin (Torino), Piacenza and Ferrara. It is connected to Milan through a net of channels called navigli, which Leonardo da Vinci helped design. Near the end of its course, it creates a wide delta (with hundreds of small channels and five main ones, called Po di Maestra, Po della Pila, Po delle Tolle, Po di Gnocca and Po di Goro) at the southern part of which is Comacchio, an area famous for eels. The Po valley was the territory of the Roman Cisalpine Gaul, divided in Cispadane Gaul (South of the Po) and Transpadane Gaul (North of the Po).