Pinnacle Glacier is located on the west slopes of Mount Adams a stratovolcano in Gifford Pinchot National Forest in the U.S. state of Washington. The glacier descends from approximately to a terminus near . Pinnacle Glacier lost 7 percent of its surface area between 1904 and 2006.
Pinnacle Glacier was named by Harry Fielding Reid during his survey of Mount Adams' glaciers with C. E. Rusk in 1901.