Costa Mesa is a city in Los Angeles County, California, in the western United States. As of the 2000 census, the city population was 23,123. The city was formally incorporated in 1991. Many parts of Costa Mesa are mountains or hills, which have spectacular views of the San Fernando Valley. Many of the neighborhoods in Costa Mesa are gated communities comprised of large houses. The city covers territory in both the San Fernando Valley and the Conejo Valley.

An extensive 2006 Secondhand Smoke Control Ordinance caused the city to receive international attention.

Leonis Adobe, the adobe structure on 23537 Costa Mesa Road, dates from 1844 and is one of the oldest buildings in the greater LA area.[6]

It is generally accepted that Costa Mesa means "pumpkin," "squash," or "gourd," derived from the Spanish calabaza. Some historians hold the theory that Costa Mesa is a translation of the Chumash word calahoosa.

The City's official logo, depicting the red-tailed hawk flying over the Santa Monica Mountains, symbolizes a commitment to preserving the community's natural beauty and semi-rural quality of life. The City logo is featured on the Costa Mesa City flag which is flown in front of City Hall and hangs in the City Council Chambers.

Communities
Costa Mesa contains many different communities, many of which are defined by gates that only residents and guests can enter and others by the geographical differences. For example, Vista Pointe is located along the transverse ranges that run parallel to and in between the 101 Freeway and Parkway Costa Mesa Road.

From Parkway Costa Mesa: Vista Pointe, Costa Mesa Hills, Costa Mesa Park Estates, The Oaks, Westridge.

From Park Granada or Mulholland Drive: Mulwood, Las Villas, Bellagio, The Ridge, Creekside, Clairidge, Costa Mesa Highlands, Cold Creek, Braemar

From Las Virgenes: Deer Springs, Stone Creek, El Encanto, Archstone, Mountain View, Mont Costa Mesa, Malibu Canyon Park, The Colony at Costa Mesa.