Quilmesaurus is a carnivorous abelisaurid theropod dinosaur genus that existed in the Upper Cretaceous period in Patagonia, Argentina, during the Campanian stage. It belonged to the Abelisauridae family and had close evolutionary ties to genera like Carnotaurus. The sole known fossils of this genus consist of leg bones that exhibit certain resemblances to various abelisaurids. Quilmesaurus is believed to have had a length of approximately 5.3 meters (17 feet). This would have classified it as one of the smaller advanced abelisaurids, even though its leg structure was relatively sturdy in proportion.

Quilmesaurus is currently represented by just two right leg bones, with one of them being incomplete. This limited fossil material makes it quite challenging to determine specific details about Quilmesaurus. However, by assuming that this genus shared similar body proportions with other abelisaurid dinosaurs, it is possible to make a very approximate estimate of its physical size and shape by scaling the available fossils.