Orange County is a county located in the Los Angeles metropolitan area in Southern California, United States. As of the 2020 census, the population was 3,186,989, making it the third-most-populous county in California, the sixth-most-populous in the United States, and more populous than 19 American states and Washington, D.C. Although largely suburban, it is the second-most-densely-populated county in the state behind San Francisco County. The county's three most-populous cities are Anaheim, Santa Ana, and Irvine, each of which has a population exceeding 300,000. Santa Ana is also the county seat. Six cities in Orange County are on the Pacific coast: Seal Beach, Huntington Beach, Newport Beach, Laguna Beach, Dana Point, and San Clemente.

Greater Los Angeles is the most populous metropolitan area in the U.S. state of California, encompassing five counties in Southern California extending from Ventura County in the west to San Bernardino County and Riverside County in the east, with Los Angeles County in the center, and Orange County to the southeast. The Los Angeles–Anaheim–Riverside combined statistical area (CSA) covers 33,954 square miles (87,940 km2), making it the largest metropolitan region in the United States by land area. The contiguous urban area is 2,281 square miles (5,910 km2), whereas the remainder mostly consists of mountain and desert areas. With a population of 18.4 million in 2024, it is the second-largest metropolitan area in the country, behind New York, as well as one of the largest megacities in the world.