Cibin (; ) is a river in central Romania, in the south part of Transylvania. Its source is in the Cindrel Mountains (known also as Cibin Mountains) of the Southern Carpathian Mountains. The river is formed at the confluence of two headwaters: Râul Mare and Râul Mic. The river flows entirely in Sibiu County. The source is close to the highest peak in the Cibin Mountains.
It is an important tributary of the river Olt, flowing into this close to Tălmaciu, in the immediate vicinity of the Podu Olt railway station. Its total length is of 82 km.
The river forms the depression ( Sibiu Depression) in which lies the city of Sibiu, through which it flows. Close to the mountains, the river flows through the Mărginimea Sibiului area, known for its strong Romanian traditions. Two of the biggest communes of Sibiu County – Gura Râului and Orlat – are situated on the river banks.
The economical importance or the river comes from the dam close to Gura Râului, which, besides generating electrical power, represents the biggest source of drinking water for the city of Sibiu. Also a few construction aggregate quarries stations are situated on the river.