Paranthropus aethiopicus is an extinct species of robust australopithecine from the Late Pliocene to Early Pleistocene of East Africa about 2.7–2.3 million years ago.

P. aethiopicus is known primarily by the skull KNM WT 17000 from West Lake Turkana, Kenya, as well as some jawbones from Koobi Fora; the Shungura Formation, Ethiopia; and Laetoli, Tanzania.

In 1968, French palaeontologist Camille Arambourg and Breton anthropologist Yves Coppens described "Paraustralopithecus aethiopicus" based on a toothless mandible (Omo 18) from the Shungura Formation, Ethiopia.

[3] In 1985, the skull KNM WT 17000 dating to 2.5 million years ago was reported from Koobi Fora, Lake Turkana, Kenya, by anthropologists Alan Walker and Richard Leakey.

[9] The genus Paranthropus (from Ancient Greek παρα para beside or alongside, and άνθρωπος ánthropos man,[10] otherwise known as "robust australopithecines") typically includes P. aethiopicus, P. boisei, and P. robustus.

P. aethiopicus is the earliest member of the genus, with the oldest remains, from the Ethiopian Omo Kibish Formation, dated to 2.6 million years ago (mya) at the end of the Pliocene.

[12] P. aethiopicus is only confidently identified from the skull KNM WT 17000 and a few jaws and isolated teeth, and is generally considered to have been ancestral to P. boisei which also inhabited East Africa, making it a chronospecies.

The jaws are the main argument for monophyly, but such anatomy is strongly influenced by diet and environment, and could in all likelihood have evolved independently in P. boisei and P. robustus.

British geologist Bernard Wood and American palaeoanthropologist William Kimbel are major proponents of monophyly, and against include Walker.

The combination of a tall face, thick palate, and small braincase caused a highly defined sagittal crest on the midline of the skull.

[8] KNM-WT 16005 is quite similar to the Peninj Mandible assigned to P. boisei, exhibiting postcanine megadontia with relatively small incisors and canines (based on the tooth roots) and large cheek teeth.

[4][8] In general, Paranthropus are thought to have been generalist feeders, with the heavily built skull becoming important when chewing less desirable, lower quality foods in times of famine.

Unlike P. boisei which generally is found in the context of closed, wet environments, P. aethiopicus seems to have inhabited bushland to open woodland habitats around edaphic (water-logged) grasslands.