The Santerno is a river in Romagna in northern Italy. It is the major tributary of the Reno River. In Roman times, it was known as the Vatrenus (small Renus), although, in the Tabula Peutingeriana, it was already identified as the Santernus.It rises near the Futa Pass, at 1,222 metres (4,009 ft) of elevation, in the Apennine ridges facing the plateau of Firenzuola in the province of Florence.