| Named By: | Altangerel Perle, Mark A. Norell & Jim Clark in 1999 |
| Time Period: | Late Cretaceous, 89 Ma |
| Location: | Mongolia, Dornogovi Province - Bayan Shireh Formation |
| Size: | Estimated 6 meters long |
| Diet: | Carnivore |
| Fossil(s): | Partial remains including vertebrae, hindlimbs, forelimbs, shoulder, ribs, as well as an upper jaw fragment of the premaxilla with teeth |
| Classification: | | Chordata | Reptilia | Dinosauria | Saurischia | Theropoda | Dromaeosauridae | Eudromaeosauria | Dromaeosaurinae | |
Achillobator ( a-KILL-a-BAY-tohr) is a dromaeosaurid theropod dinosaur that lived roughly 98 to 83 million years ago during the Late Cretaceous in what is now Mongolia, in Asia. It was among the largest dromaeosaurs; the holotype and only known individual of Achillobator is estimated at 5 to 6 m (16.4 to 19.7 ft) long. Achillobator was a moderately-built, ground-dwelling, bipedal carnivore. It would have been an active predator, hunting with the enlarged, sickle-shaped claw on the second toe.