City in Orange County, southwestern California, USA, north of Newport Beach and the Pacific Ocean, and just south of Santa Ana; population (1990) 96,400. Industries include electronics, printing, and boatbuilding.A 19th-century market-garden farming area that became a residential and cultural centre, it is home to Southern California College (1920), Orange Coast College (1947), and the Orange County Fairgrounds. Costa Mesa is noted for its cultural facilities, which include the Orange County Performing Arts Center and the Pacific Amphitheatre. The South Coast Plaza is a well-known, expensive shopping mall.