The Buzău River is a river in eastern Romania, tributary of the Siret River. Its total length is 302 km. Its source is in the south-eastern Carpathian Mountains, east of Braşov. The Buzău flows through the Romanian counties Braşov, Covasna, Buzău and Brăila. It flows into the Siret close to its confluence with the Danube, west of Galaţi.

The river Buzău gives its name to two urban municipalities: the city of Buzău (Buzău county seat) and the town of Întorsura Buzăului, in the Covasna county. Întorsura Buzăului (which means Buzău's Turning in Romanian) gets its name from being located near a large turn that the river takes. It initially flows northwards, but takes a sudden turn towards the south-east near the town.

The river Сâlnău ais the major tributary to the river Buzău: