Ontario Hot Springs is a hot-water well in southern San Luis Obispo County, California, United States. The geothermally heated water from the well is the central feature of a resort called Avila Hot Springs near Avila Beach. Ontario Hot Springs is about 8 mi (13 km) south of the city of San Luis Obispo along U.S. Route 101 in California. According to the U.S. Geographic Names Information System (GNIS), Ontario Hot Springs is located "along Gragg Canyon, 3.1 km (1.9 mi) east of the community of Avila Beach," at an elevation of 9 m (30 ft) above sea level. The resort is in a "level hollow surrounded by rural hills".