Willett Hot Springs, Natural hot spring in Sespe Wilderness, Ventura County, US

Willett Hot Springs is a natural thermal source in the Sespe Wilderness of Los Padres National Forest where warm mineral water flows into a constructed basin. The basin sits along the Sespe River Trail at a junction where hiking routes meet.

Willett Hot Springs lies in the Sespe Wilderness of Los Padres National Forest, north of Ojai in Ventura County. The sources record no founding date or historical events for the spring itself; the site is a natural thermal source that was later fitted with a man-made collection basin. The surrounding land is federal national forest, and the springs sit at about 858 metres in a valley running east to west.

The springs sit about 3 miles (4.8 km) from Sespe Hot Springs, which has a reputation as one of the hottest springs in California; hikers often visit both in one trip. The water collects in a man-made basin rather than a natural pool, so bathers share a constructed soaking spot in the Sespe Wilderness.

A National Forest Adventure Pass is required for parking at the Piedra Blanca trailhead, and the hike typically takes 2 to 3 days round trip depending on pace. Bring sufficient water, food, and camping gear since the trail passes through remote terrain with few services.

The pool is a man-made collection basin added to the natural spring, not a drilled or built spa. The nearest comparable soak, Sespe Hot Springs, lies about 3 miles (4.8 km) away and holds a reputation as one of the hottest springs in California. The site sits at roughly 858 m (2,815 ft) in a valley running east to west.