Santa Ana /ˌsæntə ˈænə/ (Spanish for ‘Saint Anne’) is the second most populous city and the county seat of Orange County, California, in the Los Angeles metropolitan area. The United States Census Bureau estimated its 2019 population at 332,318, making Santa Ana the 57th-most populous city in the United States.

Santa Ana is in Southern California, adjacent to the Santa Ana River, about 10 miles (16 km) from the coast. Founded in 1869, the city is part of the Greater Los Angeles Area, the second-largest metropolitan area in the United States, with almost 18 million residents in 2010. Santa Ana is a very densely populated city, ranking fourth nationally in that regard among cities of over 300,000 residents (trailing only New York City, San Francisco, and Boston). In 2011, Forbes ranked Santa Ana the fourth-safest city of over 250,000 residents in the United States. Santa Ana’s northwestern and southern edges are part of the two largest commercial clusters in Orange County: the Anaheim–Santa Ana edge city and the South Coast Plaza–John Wayne Airport edge city.

Santa Ana lends its name to the Santa Ana Freeway (I-5), which runs through the city. It also shares its name with the nearby Santa Ana Mountains, and the Santa Ana winds, which have historically fueled seasonal wildfires throughout Southern California. The current Office of Management and Budget (OMB) metropolitan designation for the Orange County Area is Santa Ana–Anaheim–Irvine, California.

Approximately four-fifths Latino, the New York Times characterizes Santa Ana as the “face of a new California, a state where Latinos have more influence in everyday life — electorally, culturally and demographically — than almost anywhere else in the country.”