Piegan Glacier is in Glacier National Park in the U.S. state of Montana. The glacier is situated in a cirque on the southeast slope of Piegan Mountain and just below the summit at an elevation between above sea level. The glacier covered an area of approximately in 2005, a 10 percent reduction in its surface area since 1966. Comparing images of the glacier taken in 1930 with those from 1998, indicates that the glacier experienced relatively little change during that period.