| Lake Merwin | |
| Location: | Clark / Cowlitz counties, Washington, United States |
| Coords: | 45.9833°N -150°W |
| Type: | reservoir |
| Inflow: | Lewis River |
| Outflow: | Lewis River |
| Catchment: | 731sqmi |
| Basin Countries: | United States |
| Area: | 3921acres |
| Max-Depth: | 190m (620feet)[1] |
| Volume: | 422400sigfig=3NaNsigfig=3[2] |
| Shore: | 32miles |
| Pushpin Map: | Washington#USA |
| Pushpin Map Alt: | Location of Lake Merwin in Washington, USA. |
| Reference: | [3] |
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.[3]