|Location||Clark / Cowlitz counties, Washington, United States|
|Primary inflows||Lewis River|
|Primary outflows||Lewis River|
|Catchment area||731 square miles (1,890 km2)|
|Basin countries||United States|
|Surface area||3,921 acres (15.9 km2)|
|Max. depth||190 m (620 ft)|
|Water volume||422,400 acre-feet (0.521 km3)|
|Shore length1||32 mi (51 km)|
|1 Shore length is not a well-defined measure.|
Lake Merwin is a reservoir on the Lewis River in the U.S. state of Washington. It lies on the border between Clark County and Cowlitz County. It was created in 1931 with the construction of Merwin Dam.
- U.S. Geological Survey Geographic Names Information System: Lake Merwin
- Merwin Dam Archived 2011-07-16 at the Wayback Machine, NPDP Dam Directory
- "Merwin Lake -- Clark County". Department of Ecology, State of Washington. Retrieved 20 December 2014.
- "Reservoirs in the United States" (PDF). United States Geological Survey. Retrieved 20 December 2014.