In terrestrial zoology, megafauna (Ancient Greek megas "large" + New Latin fauna "animal") are "giant", "very large" or "large" animals. The most common thresholds used are 44 kilograms (100 lb) or 100 kilograms (220 lb). This thus includes many species not popularly thought of as overly large, such as white-tailed deer and red kangaroo, and for the lower figure, even humans.

In practice the most common usage encountered in academic and popular writing describes land animals roughly larger than a human which are not (solely) domesticated. The term is especially associated with the Pleistocene megafauna — the giant and very large land animals considered archetypical of the last ice age such as mammoths. It is also commonly used for the largest extant wild land animals, especially elephants, giraffes, hippopotamuses, rhinoceroses, elk, condors, etc. Megafauna may be subcategorized by their trophic position into megaherbivores (e.g. elk), megacarnivores (e.g. lions), and more rarely, megaomnivores (e.g. bears).

Monsters We Met is a documentary produced by the BBC and later aired on Animal Planet in 2004 (under the title, Land of Lost Monsters). The show used computer-generated imagery to recreate the life of the giant animals that lived during the last ice age and explains how early humans encountered them. It also features humans as the main reason to the extinction of all great animals. It was narrated by Ian Holm.

It starts with mammoths living during the Ice Age. It also shows how humans became top predators and started hunting mammoths. We also had to compete with other predators like the Short-faced Bear and the Saber-toothed cats. We destroyed them by depleting their food supply, and making them starve to death.

It starts by showing how humans migrated to Australia. We also hunted the native wildlife. We encountered the huge birds and the giant lizard, megalania. The reptiles kill two humans and they plan on burning the fields to kill the giant lizard. We then start to colonize other people.