The Big 5 refers to 5 African animals that were historically considered the most difficult for big game hunters to hunt: the lion, leopard, rhinoceros, elephant, and Cape buffalo. These large animals were challenging to hunt due to their size, strength, and ferocity when threatened. The term was coined by big game hunters to refer specifically to these 5 animals, rather than other iconic African species like the hippo, zebra, or giraffe.