Tehama is one of the 58 counties in the state of California. It was created in 1856 from parts of Butte, Colusa, and Shasta counties. As of the 2010 census the population was 63,463, up from 56,039 in 2000. The county seat and largest city is Red Bluff.
The county covers 2,962.27 square miles (7,672.2 km2), of which 2,950.99 square miles (7,643.0 km2) is land. It is bordered by Shasta County to the north, Plumas County to the east, Glenn and Butte counties to the south, Mendocino County to the southwest and Trinity County to the west.