Lyman Glacier is located on the north slopes of Mount Adams a stratovolcano in Gifford Pinchot National Forest in the U.S. state of Washington. The glacier is also within the Yakama Indian Reservation and descends from near the summit of Mount Adams at approximately to a terminus near . Below the glacier splits into three distinct lobes. Lyman Glacier has been in a general state of retreat for over 100 years and lost 34 percent of its surface area between 1904 and 2006.