The Hotlum Glacier is a glacier situated on the northeast flank of Mount Shasta, in the US state of California. It is the largest and most voluminous glacier in California, although not as thick or long as the nearby Whitney Glacier. The Hotlum Glacier flows from a large cirque on the northeast side of Mount Shasta's main summit below the Hotlum Headwall at roughly 13,600 ft (4,100 m).