Hill Canyon is a deep canyon in the western Simi Hills and within northern Newbury Park and Thousand Oaks, in Ventura County, southern California]].
The Arroyo Conejo Nature Preserve includes the central canyon area, and is part of the Conejo Canyons Open Space. It has trails connecting it to Santa Rosa Valley County Park at the canyon's mouth, to Wildwood Regional Park east of the canyon, and to Rancho Conejo Playfields southwest of the canyon.
The canyon separates the Conejo Grade area and westernmost Simi Hills from the Mount Clef Ridge to the east. It was formed by Arroyo Conejo (creek) flowing down through the Simis from the higher Conejo Valley to the lower Santa Rosa Valley, where the creek merges with Arroyo Santa Rosa and becomes Conejo Creek.
It is located in an area locally known as La Barranca (Spanish for canyon).
It is a deeply eroded canyon at the foothills of dramatic ridgelines and volcanic outcroppings on the Mount Clef Ridge. Hill Canyon is part of the Conejo Canyons Open Space, which is owned and operated by the Conejo Open Space Foundation (COSF).
The canyon is situated east of the Conejo Grade in Camarillo, CA, and is immediately west of the Mount Clef Ridge of Wildwood Regional Park in Thousand Oaks. Hiking trails and bridges connects these cities from trailheads found for instance in Wildwood Regional Park, Rancho Conejo Playfields and Santa Rosa County Park. Hill Canyon Trail is the primary trail and connects to the Hawk Canyon Trail, Western Plateau Trail, Arroyo Conejo Trail, Lynnmere Trail, and the Canyon Overlook Trail, which climbs to the top of the Mount Clef Ridge from Santa Rosa Valley.