San Bernardino County is a county in the U.S. state of California. As of the 2000 census, the population was 1,709,434. As of 2009, the population was estimated by the California Department of Finance to have grown to 2,060,950. San Bernardino County is the largest county in the continental United States by area (Alaska has four larger county equivalents), and is larger in area than each of the nine smallest states.

Located in the southeast of the state of California, the thinly populated deserts and mountains of this vast county stretch from the outskirts of the densely populated Riverside-San Bernardino Area to the Nevada border and the Colorado River.

The county seat is San Bernardino. The county is considered to be part of the Inland Empire region and is also the only county in California bordered by both Nevada and Arizona, and is one of only two counties in California bordering more than one US state (the other being Modoc County, bordering Nevada and Oregon in the northeast corner of the state).