The John Muir Trail (JMT) is a long-distance trail in the Sierra Nevada mountain range of California, running 211 miles (340 km) from the Happy Isles trailhead in Yosemite Valley south to Trail Junction on Mt. Whitney on the border of Sequoia National Park and Inyo National Forest. For about 160 miles (257 km), the trail follows the same footpath as the much longer Pacific Crest Trail. It is named for naturalist John Muir.

The official length of the JMT (as stated by the USGS) is 211 miles. When this distance was calculated by the USGS, they did not take into consideration the amount of distance of ascent and descent. It is estimated that, when hiking north to south, the amount of ascent of the JMT is just over 46,000 feet and the total decent is just over 38,000 feet-- for a total of about 84,000 feet. If you divide this figure by 5,280 feet (the number of feet in a mile), the total mileage of ascent and decent is about 16 miles. Therefore the actual mileage of hiking the JMT is about 227 miles. From Trail Crest to the summit of Mt. Whitney is two miles and from the summit down to Whitney Portal is 11 miles. The total distance from Happy Isles to the summit of Mt. Whitney and down to Whitney Portal is about 240 miles.

Construction of the JMT began a year after Muir's death in 1915 with a $10,000 grant from the California legislature, and was completed in 1938 with the construction of the "Golden Staircase" section of the trail northwest of Mather Pass.

From its northern terminus in Yosemite Valley, the trail runs northeast to Tuolomne Meadows, passing near Half Dome, then, running parallel to the main range of the Sierra Nevada, southeast through Yosemite National Park, Inyo and Sierra national forests (including the John Muir and Ansel Adams wilderness areas), Devils Postpile National Monument, Kings Canyon National Park, and Sequoia National Park. From the southern terminus of the John Muir Trail at the summit of Mt. Whitney, an additional 11-mile (18-km) hike is required to reach the nearest trailhead at Whitney Portal, thus making an end-to-end traverse of the trail effectively 222 miles (357 km).

With the exception of the first nine miles at the northern end climbing out of Yosemite Valley, the elevation of the John Muir Trail seldom dips below 8,000 feet (2438 m). The trail crosses six passes in excess of 11,000 feet (3353 m): from north to south, Donohue Pass, Muir Pass, Mather Pass, Pinchot Pass, Glen Pass, and Forester Pass (the highest, at 13,153 feet (4009 m).