Glen Canyon Park, Natural urban park in Glen Park district, San Francisco, US.

Glen Canyon Park is a city park in San Francisco occupying about 70 acres (28 ha) along a deep canyon adjacent to Glen Park, Diamond Heights, and Miraloma Park. The canyon walls are extremely steep, with slopes approaching a 1:1 length-to-height ratio, and elevations range from about 225 feet (69 m) at the south end to 575 feet (175 m) at the north end and eastern rim. Free-flowing Islais Creek runs along the canyon bottom, surrounded by willow thickets, and reddish layered Franciscan chert outcrops show visible banding.

Adolph Sutro bought 76 acres of the canyon in the 1850s and named it Gum Tree Ranch after the blue gum eucalyptus he planted. On March 19, 1868, the Giant Powder Company began making dynamite there under licence from Alfred Nobel, the first commercial dynamite production in the United States; the plant stood near today's recreation center at the south end and did not last long.

Islais Creek, named after the wild cherry islay, runs through the canyon and is the largest remaining creek in San Francisco with public access. Local climbers treat the chert outcrops as one of the best bouldering sites near the city, and the grassland supports breeding pairs of red-tailed hawks and great horned owls.

The grounds are accessible on foot from the Glen Park neighborhood and offer multiple entry points for visitors. Sturdy footwear is recommended because the paths can be uneven and some sections may be steep or slippery.

Islais Creek flows through the park grounds and creates a streamside area with willow trees, horsetails, and red columbine plants. This creek and the vegetation around it form their own small world within the larger park.