Diamond Lake is an unincorporated community in Pend Oreille County, Washington, United States located southwest of Newport, Washington. The Diamond Lake community is built around Diamond Lake.
Diamond Lake is a natural lake located in the area north of U.S. Route 2.
The average depth of the lake is deep with a maximum depth of . Diamond Lake offers year-round fishing and has a population of largemouth bass, yellow perch, bullheads, rainbow and brown trout. A cooperative net pen project releases 12,500 rainbow and brown trout. Approximately 200 rainbow trout surplus broodstock are farmed in Diamond Lake annually.