Let's not slowly build suspense. Every fast list should start with the cheetah. These guys can reach speeds of 59 mph (95 kph) in seconds [source: Yong]. A somewhat surprising second-place contender for fastest? The pronghorn antelope, which can rival cheetahs with a speed of 53 mph (85 kph) [source: National Geographic]. So there you go: the speediest animals on the planet.
Not so fast.
If we're counting water-based animals, the sailfish is our clear winner, reaching 68 mph (110 kph) -- and that's just what they've been clocked at when bursting out of the water [sources: National Geographic, Sagong et al.].
Now look up. The peregrine falcon cackles at the cheetah and sailfish eating its dust. When it's hunting for smaller birds, the falcon can dive -- at 200 mph (320 kph) -- to strike its target [sources: National Geographic, Ponitz et al.]. The peregrine wins the title of fastest animal by a long shot.