Oreopithecus bambolii, or swamp ape, is a hominoid, or hominid (there is some controversy among the informed), species whose fossils have been found in Italy (Tuscany and Sardinia) and in East Africa.

Their habitat appears to have been swampy, and not savanna or forest. The fossils are sufficient to indicate that there was a lumbar curve, implying some adaptation to upright walking, in distinction to otherwise similar species known from the same period. Since the fossils have been dated to about 8 million years ago, this represents an unusually early appearance of upright posture, lending itself to the aquatic ape theory of human bipedalism, especially in conjunction with other evidence of a possible earlier date for the evolution of hominids, such as the six to seven million year old, very human-looking Toumai skull.

Some have suggested this requires a revision of the current consensus on the timing of bipedality in human developmental history, but there is little agreement on this point among paleontologists. For the moment, this species is a considerable anomaly, and may represent an independent development of bipedality other than that which led to humans, and which came to a dead end some time later. More fossil discoveries may help settle this and other questions.

The name quickly inspired the commonly used name for the species among paleontologists, which is, inevitably, Cookie Monster.