Wakaleo (Diyari waka, "little", "small"; and Latin leo, "lion")[1] is an extinct genus of medium-sized thylacoleonids that lived in Australia in the Late Oligocene and Miocene Epochs.

[2] The smallest known species of Wakaleo, it lived in Australia about 25 million years ago, from the late Oligocene to middle Miocene, and was approximately the size of a cat.

To date W. pitikantensis, Wakaleo schouteni and "Priscileo' roskellyae are the most ancient phylogenies of the Thylacoleonidae and presumed to have diverged during the early to middle Oligocene epoch.

[3] The description of the species was published in 2017, the collaborating authors Anna Gillespie, Mike Archer and Suzanne Hand working on the PANGEA research project based at the University of New South Wales.

The holotype is a largely complete skull retaining some teeth and alveoli, with other materials such as the lower jaw and a humerus associated with the new species as paratypes.

[3][8] Another estimate using regression equations previously used in calculations of body size for Thylacoleo carnifex, a very large carnivore, resulted in a value around 5 kg that the describing authors considered too small.

[3] The distribution of the species included the Riversleigh World Heritage Area in the northwest of Queensland, at sediments dated to the later Oligocene to early Miocene.

The humerus morphology is proposed to support this conception as a scansorial and arboreal predator, being similar to the structures of the arm and shoulder in species such as Phascolarctos cinereus, the related koala, and spotted cuscus Spilocuscus maculatus.