The Conejo Valley is a region spanning both southeastern Ventura County and northwestern Los Angeles County in Southern California, United States. It was discovered in 1542 by Portuguese explorer Juan Rodríguez Cabrillo, and eventually became part of the Rancho El Conejo land grant by the Spanish government (in Spanish conejo means "rabbit", and refers to the rabbits common to the region, specifically the Desert Cottontail and Brush Rabbit species). It is located in the northwestern part of the Greater Los Angeles Area.

The area is bordered by the San Fernando Valley and the city of Los Angeles to the east, Simi Hills to the north, Las Posas Hills and the Santa Rosa Valley to the northwest, Conejo Mountain (also known as Conejo Hills) and Oxnard Plain to the west, and the Santa Monica Mountains and Malibu to the south, the Westside, and Pacific Ocean beyond it. The valley is located in the Santa Monica Mountains on an elevated area.

Many high-tech companies, particularly those in biotechnology, including Amgen, Baxter, General Dynamics Corporation, and Rockwell International are prevalent in the area. It also includes many other tech corporations, especially dot com companies and telecommunications like Verizon and Verizon Wireless. It also is home to many healthcare and other various companies like WellPoint, J.D. Power and Associates, Volkswagen, Audi, THQ, and cosmetics leader Jafra Cosmetics. Although the region is predominantly white with a large Hispanic minority, there is a small, but growing, Asian minority in the region.