Aviatyrannis is a genus of carnivorous tyrannosauroid theropod dinosaur from the Kimmeridgian stage of the Late Jurassic, found in Portugal. The only species is Aviatyrannis jurassica (meaning "tyrant's grandmother from the Jurassic") and its holotype was dated as being about 155 million years old: it is one of the oldest tyranosauroids ever found.
The holotype material consists of a right illium, a partial right illium, a right ischium, three teeth of the premaxila and thirteen teeth of the maxila and dentary.
There is, however, some speculation that Aviatyrannis is actually a junior synonym of Stokesosaurus, and further fossil material may reveal the answer once and for all. Regardless of what may happen with the genus of Aviatyrannis in the future, the fossils from Portugal do prove that the early tyrannosaurs did find their way to Europe, probably from North America. This in turn goes some way to explaining the presence of Eotyrannus, a later tyrannosaur from the Early Cretaceous that was discovered in the British Isle's.