Rainier, Mount, a dormant volcano in the Cascade Range of southwestern Washington. It is the central feature of Mount Rainier National Park. Columbia Crest, the highest of the volcano's three peaks, is the highest point in the state, rising 14,410 feet (4,392 m) above sea level. An extensive system of glaciers radiates from the snowy summit. Among the most easily visited of the 26 active glaciers are Emmons, Nisqually, and Paradise. The meadows on Mount Rainier's lower slopes are noted for the abundance and variety of their summer wild flowers.

Mount Rainier is one of a chain of volcanoes in the Pacific Northwest. It has not erupted for many years; however, there is minor activity, such as the emission of gas and steam through vents in the crater. Captain George Vancouver discovered Mount Rainier in 1792. The national park was established in 1899.