|Sön, Syun River|
|Mouth||Nizhnekamsk Reservoir, Belaya River (Kama basin), Bashkortostan|
|Basin countries||Bashkortostan and Tatarstan, Russia|
|Length||209 km (130 mi)|
|Avg. discharge||14.8 m3/s (520 cu ft/s)|
|Basin area||4,500 km2 (1,700 sq mi)|
The Syun (Bashkir: Сөн, Russian: Сюнь, Tatar Cyrillic: Сөн, Latin: Sön) is a river in Bashkortostan and Tatarstan, Russian Federation, a left-bank tributary of the Belaya River (Kama basin). It is 209 kilometres (130 mi) long, of which 74 kilometres (46 mi) are in Tatarstan. Its drainage basin covers 4,500 square kilometres (1,700 sq mi). Major tributaries in Tatarstan are Kalmiya, Sikiya, Terpelya, Bezyada, and Sharan in Bashkortostan. The maximal water discharge is 655 cubic metres per second (23,100 cu ft/s) (1979), and the maximal mineralization 500 to 1000 mg/l. Average sediment at the mouth per year is 120 millimetres (4.7 in). Drainage is regulated. Since 1978 it is protected as a "natural monument of Tatarstan".