Rainbow Mountain, Stratovolcano in Siskiyou County, California, United States.

Rainbow Mountain is a stratovolcano at the southern end of the Cascade Range in Siskiyou County, California, standing between Mount Shasta and Medicine Lake Volcano. It is built of andesitic and dacitic rocks produced during the Early Pleistocene subepoch, and its last known eruption is also of Pleistocene age.

The volcano formed during the Early Pleistocene period through repeated eruptions of andesitic and dacitic rock. Its development spans millions of years of sustained volcanic building.

The sources record no cultural traditions, ceremonies or naming history for Rainbow Mountain; the only documented facts are geological. Its andesitic and dacitic rocks were produced during the Early Pleistocene, and its last known eruption is also of Pleistocene age. Visitors today find no trails, signs or facilities, so the mountain is read through its rock layers rather than through any cultural use.

There are no marked trails, facilities or visitor infrastructure on the volcano; access is cross-country through the surrounding national forest. The andesitic and dacitic slopes lie between Mount Shasta and Medicine Lake Volcano, so route-finding and snow conditions should be checked before setting out. The nearest lodging and services are in the town of Mount Shasta.

The mountain ranks among the highest peaks in the area and offers views across multiple national forest territories from its summit. This position allows hikers to take in the diversity of volcanic landscapes in the region all at once.