Machairasaurus is a genus of oviraptorid dinosaur which was found in the Bayan Mandahu Formation, China, dating to the late Cretaceous period.

Based on two of these a new genus was named and described by Nicholas Longrich, Philip Currie, and Dong Zhiming in 2010 with the type species Machairasaurus leptonychus.

The specific name is derived from Greek λεπτός (leptos), "slender", and ὄνυξ (onyx), "claw".

[1] The holotype, IVPP V15979, was found in layers of the Bayan Mandahu dating from the late Campanian.

The describers established a single autapomorphy, unique derived trait: the hand claws are very elongated and blade-like in side view, with a length four times that of the joint height.