The Thylacine (Thylacinus cynocephalus, ) was the largest known carnivorous marsupial of modern times. Native to Australia and New Guinea, it is thought to have become extinct in the 20th century. It is commonly known as the Tasmanian Tiger (due to its striped back), the Tasmanian Wolf, and colloquially the Tassie (or Tazzy) Tiger or simply the Tiger. It was the last extant member of its genus, Thylacinus, although a number of related species have been found in the fossil record dating back to the early Miocene.

The Thylacine became extinct on the Australian mainland thousands of years before European settlement of the continent, but survived on the island of Tasmania along with a number of other endemic species, including the Tasmanian Devil. Intensive hunting encouraged by bounties is generally blamed for its extinction, but other contributory factors may have been disease, the introduction of dogs, and human encroachment into its habitat. Despite being officially classified as extinct, sightings are still reported.

Like the tigers and wolves of the Northern Hemisphere, from which it inherited two of its common names, the Thylacine was a top-level predator. As a marsupial, it was not related to these placental mammals, but due to convergent evolution it displayed the same general form and adaptations. Its closest living relative is the Tasmanian Devil.