Southern California (often abbreviated as So Cal) is the southern portion of the U.S. state of California. Its population is centered on the cities of Los Angeles, San Diego, San Bernardino, and Riverside. Southern California is home to nearly 24 million people and is the nation's second most populated region, behind only the BosWash Region in the Eastern United States.

There is no official definition for the northern boundary of Southern California, however, most definitions in use include all the land south of the Tehachapi Mountains, located about north of Los Angeles. Some definitions simply use the 36th parallel north which forms the northern borders of San Luis Obispo, Kern, and San Bernardino counties.

On the west of Southern California lies the Pacific Ocean; to the south is the international border between the United States and Mexico; to the east are the Mojave and Colorado Deserts and the Colorado River at the state's border with Arizona and Nevada.