Ojai is situated in a small east-west eponymous valley, north of Ventura and east of Santa Barbara. The city is approximately 745 feet (227 m) above sea level and is bordering the Los Padres National Forest to the north. It is approximately 15 miles (24 km) inland from the Pacific Ocean coast. The Ojai Valley is bounded by mountains on the north and south and is actively shaped by a web of earthquake faults. The Santa Ynez Mountains lie to the north, while Sulphur Mountain and the lower Black Mountain lie to the south. The mountains to the west of the Ojai Valley are drained by the Coyote, Matilija and Santa Ana creeks. These empty into the Ventura River. The Matilija Dam, Casitas Dam and Lake Casitas Reservoir alter the historic drainage of these creeks and the river. The creeks that drain the mountains directly north of Ojai empty into San Antonio Creek, as does Lion Canyon Creek that lies between Black Mountain and Sulphur Mountain. San Antonio Creek drains into the Ventura River just north of Casitas Springs. The Ventura River flows through the Ventura River Valley and empties into the Pacific Ocean at the city of Ventura. The Ventura River was once known for its steelhead fishing before Matilija Dam and Lake Casitas were constructed, eliminating habitat for this trout species.
The eastern part of the Upper Ojai Valley is drained by the Sisar and Santa Paula creeks. These creeks flow into the Santa Clara River at Santa Paula. The high mountains above the Ojai Valley and further east are drained by Sespe Creek, which empties into the Santa Clara River at Fillmore. In 1991, 31.5 miles of the 55-mile-long Sespe Creek was given federal Wild & Scenic River status.[38
Nordhoff Ridge, the western extension of the Topatopa Mountains, towers over the north side of the valley at more than 5,000 feet (1,500 m). Sulphur Mountain creates the southern ranges bounding the Ojai Valley, a little under 3,000 feet (910 m) in elevation. The Sulphur and Topatopa Mountains are part of the Transverse Ranges system. The Ojai Valley and the surrounding mountains are heavily wooded with oak trees.