This is a list of the fastest animals in the world, by types of animal. The peregrine falcon is the fastest bird, and the fastest member of the animal kingdom, with a diving speed of over . The fastest land animal is the cheetah. Among the fastest animals in the sea is the black marlin, with uncertain and conflicting reports of recorded speeds.
When drawing comparisons between different classes of animals, an alternative unit is sometimes used for organisms: body length per second. On this basis the 'fastest' organism on earth, relative to its body length, is the Southern Californian mite, Paratarsotomus macropalpis, which has a speed of 322 body lengths per second. The equivalent speed for a human, running as fast as this mite, would be , or approximately Mach 1.7. The speed of the P. macropalpis is far in excess of the previous record holder, the Australian tiger beetle Rivacindela eburneola, which is the fastest insect in the world relative to body size, with a recorded speed of , or 171 body lengths per second. The cheetah, the fastest land mammal, scores at only 16 body lengths per second. Body mass can also be used to compare speed between species on a relative basis. Under this parameter the fastest animal for its body mass is the cheetah, followed by the pronghorn.
Through studies of pronghorn running on treadmills, it has been estimated that the maximum speed that could be achieved using mainly oxygen would be 72 km/h (45 mph) for about 10 minutes, so higher speeds such as those reported in Thomson's gazelles, springboks, pronghorn and cheetahs require adaptations for principal use of anaerobic energy sources such as glycogen and creatine phosphate, and could therefore be maintained for only 30-45 seconds when these energy sources are depleted. High acceleration also requires the use of anaerobic energy sources.
Due to physical constraints, fish may be incapable of exceeding swim speeds of . The larger reported figures below are therefore highly questionable: