Trinity County is a county located in the northwestern portion of the U.S. state of California. Trinity County is rugged, mountainous, heavily forested, and lies along the Trinity River within the Salmon and Klamath Mountains. It is also one of three counties in California with no incorporated cities.

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.