Diablo Lake is a reservoir in the North Cascade mountains of northern Washington state, United States. Created by Diablo Dam, the lake is located between Ross Lake and Gorge Lake on the Skagit River at an elevation of above sea level. Diablo Lake is part of the Skagit River Hydroelectric Project and managed by Seattle City Light. Diablo Lake Trail, designated a National Recreation Trail in 1981, runs for along the lake's northern shore.