Lake Steilacoom is a reservoir approximately 4 km (2.5 mi) southwest of Tacoma in Pierce County, Washington, United States.

The reservoir was created in 1853 when Andrew Byrd built a dam across Chambers Creek, flooding what had previously been a small pond in a wetland.

A public boat launch can be found on the eastern shore in Edgewater Park.

The Interlaaken Bridge was built in the 1920s over a narrow in the lake; it was closed in 2024 after "rapid deterioration" was discovered in the wood beams.

[2] According to Nisqually tribe legend, the lake was possessed by an evil female monster known as Whe-atchee.