Sayansk () is a town in Irkutsk Oblast, Russia, located on the Oka River (Angara River's basin) northwest of Irkutsk. Population:
Sayansk was founded in 1970. It was granted urban-type settlement status in 1975 and town status in 1985.
Within the framework of administrative divisions, it is incorporated as the Town of SayanskâÂÂan administrative unit with the status equal to that of the districts. As a municipal division, the Town of Sayansk is incorporated as Sayansk Urban Okrug.