The Santa Barbara Channel is a portion of the Southern California Bight and separates the mainland of California from the northern Channel Islands. It is generally south of the city of Santa Barbara, and west of the Oxnard Plain in Ventura County. It trends east-west, is approximately 130 kilometres long and averages about 45 kilometres across, becoming narrowest at its easternmost extremity where Anacapa Island is about 30 kilometres from the mainland.