West Hills is bordered by Chatsworth and the Chatsworth Reservoir to the north, Canoga Park to the east, Woodland Hills to the south, Calabasas and Hidden Hills to the southwest, and the Simi Hills with the Upper Las Virgenes Canyon Open Space Preserve and Bell Canyon to the west.
In 1987, Los Angeles recognized the following description of the boundaries of West Hills: "Starting at the centerline intersections of Topanga Canyon Boulevard and Nordhoff Street, westward down the centerline of Nordhoff extended in a straight line to the city limits of the City of Los Angeles; thence southward, following the border of the City of Los Angeles to the centerline of Victory Boulevard; thence eastward down the centerline of Victory Boulevard to Shoup Avenue centerline; thence northward down the centerline of Shoup Avenue to the intersection of the centerline of Roscoe Boulevard; thence eastward down the centerline of Roscoe Boulevard to the centerline of Topanga Canyon Boulevard; then northward down the centerline of Topanga Canyon Boulevard to the centerline of Nordhoff Street."
Bell and Dayton creeks in West Hills are several of the headwaters of the Los Angeles River that originate in the Northwest San Fernando Valley. The Los Angeles River itself begins at the confluence of Arroyo Calabasas (Calabasas Creek) and Bell Creek in Canoga Park. These and other small creeks supply stormwater and suburban runoff water to the Los Angeles River, and several are considered year-round creeks. Although the creeks are now channeled and run within concrete walls, they do form a significant urban wildlife landscape and contribute to the population of indigenous wildlife left within the San Fernando Valley.
Both Bell Creek and Dayton Creek in particular have received attention due to their headwaters origins inside the SSFL—Santa Susana Field Laboratory in the Simi Hills. The SSFL is mandated for an environmental cleanup due to its uses as a testing center for rocket and missile engines, nuclear reactor research and fuel reprocessing, and high technology defense systems. It was also the site of a partial nuclear core meltdown in 1959. Prominent contaminants include radionuclides, VOCs-volatile organic compounds, Chromium, Lead, Benzene, and other components of rocket engine fuel and cleaning compounds.
 Pre-Spanish contact history
The present day West Hills area was the homeland of Native Americans in the Tongva-Fernandeño and Chumash-Venturaño tribes, that lived in the Simi Hills and close to Bell Creek and the local tributaries to the Los Angeles River. Native American civilizations had inhabited the San Fernando Valley for an estimated 8,000 years. The village, Hu'wam, of the Chumash-Venturaños, was located at the base of Escorpión Peak (Castle Peak) near present day Bell Canyon Park. It was a meeting and trading point for them with the Tongva-Fernandeño and Tataviam-Fernandeño people. A cave near here known as The Cave of Munits is the believed home of a mythical Chumash shaman, Munits, who was killed by an eagle after murdering the son of a Chumash chief. Escorpión Peak is one of nine alignment points in Chumash territory and is essential to maintaining the balance of the natural world.