List of dams and reservoirs in Washington

This is a list of dams and reservoirs in the U.S. state of Washington, and pertinent data. According to the Washington State Department of Ecology, as of 2020 there were 1226 dams in the state. Of 39 counties, King County had the most dams, 125. ^[1]

The largest dam in Washington, in terms of structural volume, reservoir capacity and electricity production, is the Grand Coulee Dam on the Columbia River. The tallest dam is Mossyrock Dam on the Cowlitz River, at 606 feet (185 m). The longest dam is O'Sullivan Dam on Crab Creek, at 19,000 feet (5,800 m).