Trinity Lake, previously called Clair Engle Lake, is a reservoir on the Trinity River formed by the Trinity Dam and located in Trinity County, California, United States. The dam was built by the U.S. Bureau of Reclamation. The lake's capacity is 2,447,650 acre⋅ft (3,019.13 GL), making it one of the largest reservoirs in California. The lake's surface is at 2,370 ft (720 m) above MSL. Trinity Lake captures and stores water for the Central Valley Project, which provides the Central Valley with water for irrigation and produces hydroelectric power. This lake is known for its many small arms, glassy inlets, and good water-skiing conditions.

The Trinity River is a major river in northwestern California in the United States and is the principal tributary of the Klamath River. The Trinity flows for 165 miles (266 km) through the Klamath Mountains and Coast Ranges, with a watershed area of nearly 3,000 square miles (7,800 km2) in Trinity and Humboldt Counties. Designated a National Wild and Scenic River, along most of its course the Trinity flows swiftly through tight canyons and mountain meadows.