A pika ( PY-kə; archaically spelled pica) is a small, mountain-dwelling mammal found in Asia and North America. With short limbs, very round body, an even coat of fur, and no external tail, they resemble their close relative, the rabbit, but with short, rounded ears. The large-eared pika of the Himalayas and nearby mountains is found at heights of more than 6,000 m (20,000 ft), among the highest of any mammal.

Pikas prefer rocky slopes and graze on a range of plants, mostly grasses, flowers and young stems. In the autumn they pull hay, soft twigs and other stores of food into their burrows to eat during the long, cold winter. The pika is also known as the whistling hare because of its high-pitched alarm call when diving into its burrow.

The name ‘pika’ appears to be derived from the Tungus piika, and the scientific name Ochotona is from the Mongolian word ogutun-a, оготно, which means pika. It is used for any member of the Ochotonidae (), a family within the order of lagomorphs which also includes the Leporidae (rabbits and hares). Only one genus, Ochotona ( or ), is extant within the family, covering 37 species, though many fossil genera are known. Another species, the Sardinian pika, belonging to the separate genus Prolagus, has become extinct within the last 2000 years owing to human activity.

The two species found in North America are the American pika, found primarily in the mountains of the western United States and far southwestern Canada, and the collared pika of northern British Columbia, the Yukon, western Northwest Territories and Alaska.