Glacier Peak Wilderness is a 566,057-acre (229,075 ha), 35-mile-long (56 km), 20-mile-wide (32 km) wilderness area located within portions of Chelan, Snohomish, and Skagit counties in the North Cascades of Washington. The area lies within parts of Wenatchee National Forest and Mount Baker National Forest and is characterized by heavily forested stream courses, steep-sided valleys, and dramatic glacier-crowned peaks. The dominant geologic feature of the area is 10,541-foot (3,213 m) Glacier Peak. It is the most remote major volcanic peak in the Cascade Range and has more active glaciers than any other place in the lower forty-eight states. Glacier Peak is a volcanic cone of basalt, pumice, and ash which erupted during periods of heavy glaciation.

The North Cascades are a section of the Cascade Range of western North America. They span the border between the Canadian province of British Columbia and the U.S. state of Washington and are officially named in the U.S. and Canada as the Cascade Mountains. The portion in Canada is known to Americans as the Canadian Cascades, a designation that also includes the mountains above the east bank of the Fraser Canyon as far north as the town of Lytton, at the confluence of the Thompson and Fraser Rivers.