The Nisqually Glacier is one of the larger glaciers on the southern face of Mount Rainier in the U.S. state of Washington. The glacier is one of the most easily viewed on the mountain, and is accessible from the Paradise visitor facilities in Mount Rainier National Park. The glacier is currently retreating. Measurements made at 9,200 feet (2,800 m) altitude show that glacier got 56 ft (17 m) thicker between 1994 and 1997, suggesting that it will probably begin advancing in the first decade of the 21st century. Nisqually Glacier is the source of the Nisqually River. Perhaps the longest studied glacier on Mount Rainier, Nisqually's terminal point has been measured annually since 1918. In May 1970, the glacier was measured to be moving at an average of 29 inches (740 mm) per day.
The glacier is one of four on Mount Rainier that are known to have released debris flows. Similar flows have stemmed from the Winthrop, Kautz, and South Tahoma glaciers as well.