Unenlagia, scientifically known as "Unenlagia comahuensis," is a genus of theropod dinosaur that lived during the Late Cretaceous period, approximately 90 million years ago. The name "Unenlagia" is derived from the Unenla Creek in Argentina, close to where the fossil remains were discovered. As a theropod, Unenlagia belongs to the group of carnivorous dinosaurs, characterized by their bipedal stance and predatory nature, the Dromaeosauridae.

The fossil remains of Unenlagia were first discovered in the Patagonia region of Argentina, contributing to the rich paleontological heritage of South America. Determining the body length of Unenlagia has proven challenging because only the leg length is well-established. There is uncertainty regarding whether to extrapolate it using the proportions of the low-slung Dromaeosauridae or the long-legged basal birds. As a result, estimates have ranged from a length of 3.5 meters (11 feet) to a weight of 75 kilograms (165 pounds).

Unenlagia exhibited a unique combination of features that set it apart from other theropod dinosaurs. It walked on two long and slender hind limbs, which provided it with a fast and agile means of locomotion. Its forelimbs were also highly developed and featured elongated fingers, suggesting they were adapted for grasping and manipulating objects.

One of the most distinctive characteristics of Unenlagia was the presence of feather impressions found in some fossil specimens, indicating that it was feathered. This discovery has significant implications for our understanding of the evolution of feathers in dinosaurs. The presence of feathers on Unenlagia suggests that it may have had some level of insulation, indicating that it could have maintained a relatively constant body temperature. Feathers may have also played a role in courtship displays or provided a means of communication within the social group.