The Oxnard Plain is a large coastal plain in southwest Ventura County, California bounded by the Santa Monica Mountains, the Santa Susana Mountains, and Oak Ridge (beyond which lies the Conejo Valley) to the east, the Topatopa Mountains to the north, the Santa Clara River Valley to the northeast and the Pacific Ocean to the south and west. The Oxnard Plain is also home to the western half of the Oxnard-Thousand Oaks-Ventura Metro Area which includes the cities of Oxnard, Ventura, Camarillo, Port Hueneme and Santa Paula, as well as the unincorporated towns of Channel Islands, El Rio, Montalvo, Saticoy and Somis.

The alluvial plain is home to some of the most fertile soil in the world, and as such, agriculture is one of the region's most vital and important industries. The Oxnard Plain is known for its strawberries, leading to the moniker "Strawberry Capital of the World" and the annual California Strawberry Festival, the nation's largest. (Likewise, Santa Paula is called "The Citrus Capital of the World".) Oxnard Plain is also a major producer of celery, lima beans, lettuce, tomatoes, broccoli, onions and citrus fruits, namely lemons. The Plain also produces a major proportion of the transplanted Asian vegetable crop for the US including produce such as Bok Choi.