Thornton Lakes are located in North Cascades National Park, in the U. S. state of Washington.

[2] These paternoster lakes consist of three lakes located 1 to 1.75 mi (1.61 to 2.82 km) southeast of Mount Triumph.

Thornton Lakes can be accessed on foot from a trailhead in Ross Lake National Recreation Area.

The hike of 5.2 mi (8.4 km) includes a 2,400-foot (730 m) altitude gain and a 500-foot (150 m) descent to Lower Thornton Lake.

A designated backcountry camping zone is located at Lower Thornton Lake.