The Reno ([ˈrɛːno]) is a river of Emilia-Romagna, northern Italy. It is the tenth longest river in Italy (the sixth longest of those that flow directly into the sea) and the most important of the region apart from the Po.
It has a drainage basin of about 5,000 square kilometres (1,900 sq mi). The annual average discharge at the mouth is about 95 cubic metres per second (3,400 cu ft/s); at the point the river start to flow in the Pianura Padana (Po River Plain), it amounts to about 25 cubic metres per second (880 cu ft/s).
The highest values registered at the mouth have approached 2,300 cubic metres per second (81,000 cu ft/s), but the typical value when the river is in flood is around 1,000 cubic metres per second (35,000 cu ft/s). The minimal discharge reported is 0.6 cubic metres per second (21 cu ft/s).
The river rises in the Le Lari massif of the province of Pistoia (Tuscany) at about 745 metres (2,444 ft) above sea level, from two streams that join near Le Piastre, in the comune of Pistoia. Its upper course marks the border between Tuscany and Emilia-Romagna and flows in a wooded area crossed by the Bologna-Porretta-Pistoia railway line (inaugurated in 1864 and one of the most outstanding for the time as for engineering effort).
The upper course is characterized by several artificial reservoirs whose dams are used for hydro-electric energy production. The power produced in the basin of the Reno basin is second, for Apennine rivers, only to that of the Nera-Velino in Umbria.