|• elevation||550 feet (170 m)|
|Saint George River|
|7 feet (2.1 m)|
|Length||12.5 miles (20.1 km)|
|• left||East Branch Oyster River|
|• right||West Branch Oyster River|
The Oyster River is a tributary of the Saint George River in Knox County, Maine. From its source () in Rockport, the river runs 12.5 miles (20.1 km) south and southwest to its confluence with the Saint George. Its lower third forms the border between Warren and Thomaston.