| Named By: | Richard Owen in 1859 |
| Time Period: | late Pliocene-late Pleistocene |
| Location: | Australia |
| Size: | Largest species (T. carnifex) up to 75 centimetres high at the shoulder. Smallest species (T. hilli) roughly half this size.. Average weight was between 100 and 130 kilograms, but larger individuals could approach 160 kilograms |
| Diet: | Carnivore |
| Fossil(s): | Many specimens, some of which are almost complete allowing for accurate reconstruction |
| Classification: | | Chordata | Mammalia | Marsupialia | Diprotodontia | Thylacoleonidae | |
Thylacoleo ("pouch lion") is an extinct genus of carnivorous marsupials that lived in Australia from the late Pliocene to the late Pleistocene (2 million to 46 thousand years ago). Some of these "marsupial lions" were the largest mammalian predators in Australia of that time, with Thylacoleo carnifex approaching the weight of a small lion. The estimated average weight for the species ranges from 101 to 130 kg.