Opuntia fragilis, known by the common names brittle prickly pear and little prickly pear, is a prickly pear cactus native to much of North America. It occurs in several Canadian provinces. It is known from farther north than any other cactus, occurring at as close as 8°south of the Arctic Circle, (58°N latitude) in Alberta. There is an isolated and possibly genetically unique population in Eastern Ontario known as the "Kaladar Cactus".
Brittle Prickly Pear is a small decumbent cactus that grows to a maximum height of 10 centimeters (4 in). Both the common and scientific names refer to the easily detached stem segments. This is known to be a means of plant dispersal.
Opuntia fragilis is a small, prostrate plant, rarely more than 4 inches high: joints tumid, fragile, easily detached, oval, elliptical, or subglobose, 1-2 in. long and nearly as thick as broad, bright green: areoles ¼-½ in. apart, with whitish wool and a few white to yellow bristles, which are much longer and more abundant on older joints; spines 1-4, occasionally a few small additional ones, weak, dark brown, the upper one usually longer and stronger than the others, rarely an inch in length: flowers greenish yellow, 1-1¼ inches wide: fruit ovate to subglobose. with few spines or bristles, mostly sterile, an inch or less long; seeds few and large. Rocky Mountain region from Canada to New Mexico. 
Subspecies and varieties
- Var. brachyarthra, Coult. A plant with more swollen joints, more numerous and stronger spines, smaller flowers and more spiny fruit Colorado, New Mexico.
- Var. caespitosa, Hort. Joints bright green, smaller and more crowded than in the type: flowers bright yellow. Colorado.
- Var. tuberiformis, Hort. Joints olive-green, bulbous-looking. Colorado.