Cottage Grove Lake is a reservoir on the Coast Fork Willamette River in Lane County, Oregon, United States.

[2] It was completed in 1942 as one of the 13 dams built by the United States Army Corps of Engineers in the Willamette River basin.

[2] The dam's main function, in conjunction with the Dorena Dam on the Row River, a Coast Willamette tributary, is flood control.

[1] Other functions are to supply water for irrigation and improved river navigation.

[2] The lake and its surrounds are used for recreation, including boating, camping, fishing, picnicking, and bird-watching.