It is known from a series of large jaw and skull fragments found at the Sangiran site near Surakarta in Central Java, Indonesia, alongside several isolated teeth.

Some of these finds were accompanied by evidence of tool use similar to that of Homo erectus; this is why Meganthropus was often linked with that species as H. e. palaeojavanicus.

In 2019, a study of tooth morphology found Meganthropus a valid genus of non-hominin hominid ape, most closely related to Lufengpithecus.

Koenigswald was captured by the Japanese in World War II, but managed to send a cast of the jaw to Franz Weidenreich.

Weidenreich considered acromegalic gigantism, but ruled it out for not having typical features such as an exaggerated chin and small teeth compared to the jaw's size.

The ramus portion is badly damaged, but the mandible fragment appears relatively unharmed, although details of the teeth have been lost.

As with most fossils it was heavily damaged, but given the completeness of the post facial cranium the chances of error in its reconstruction are very small.

Robinson (1953) first suggested that Meganthropus (based on the Sangiran 6 mandibular fragment) could be a Southeast Asian representative of robust australopithecines.

A similar theory was proposed by Krantz (1975) who argued that Sangiran 6 is: "entirely outside the possible size range of Homo erectus and should be classed as Australopithecus africanus" (i.e. gracile as opposed to robust australopithecine).

According to Koenigswald (1973) both robust and gracile australopithecine traits can be found in Sangiran 6: "In certain respects the lower jaw of Meganthropus combines characteristics of A. africanus (premolars) with those of A. robustus (size)."

A study by Orban-Segebarth & Procureur (1983) of the Sangiran 6 mandible also concluded: "Asiatic Meganthropus 'Sangiran 6' has marked australopithecoid traits" but Kramer and Konigsberg (1994) challenge this view.

The concept of a "mystery ape" most closely related to Lufengpithecus in the Javan Pleistocene was first raised by Russell Ciochon in 2009, though he still considered Meganthropus conspecific with H.