Hill Canyon is a deep, rugged canyon in the western Simi Hills spanning northern Newbury Park and Thousand Oaks in southern California. Formed by Arroyo Conejo cutting from Conejo Valley toward Santa Rosa Valley, it is now largely protected within Arroyo Conejo Nature Preserve and Conejo Canyons Open Space. Its steep walls, foothill slopes, and volcanic outcroppings support varied plant communities and make it an important natural corridor linking surrounding valleys and ridges. Trails connect the canyon to nearby parks and open space, making it a major destination for hiking, running, biking, and horseback riding. The canyon also contains the Hill Canyon Wastewater Treatment Plant, the area’s only developed site.