Coast Mountains, mountains in western British Columbia and southeastern Alaska. They extend from about the Yukon Territory border southeastward along the coast of the mainland to the Fraser River east of Vancouver, British Columbia. The Coast Mountains are about 900 miles (1,450 km) long and as much as 100 miles (160 km) wide.

Formed at the same time as the Sierra Nevada range in the United States, the Coast Mountains are geologically young and extremely rugged. A number of peaks exceed elevations of 10,000 feet (3,000 m); Mount Waddington, which ascends to 13,104 feet (3,994 m), is the highest peak in the Coast Mountains. Large glaciers cover the highest peaks. Numerous rivers, flowing through deep gorges, cut across the mountains. The heavily forested slopes are a major Canadian source of timber, chiefly Douglas fir and western hemlock.