Homo heidelbergensis is a species of archaic human from the Middle Pleistocene of Europe and Africa, as well as potentially Asia depending on the taxonomic convention used. The species-level classification of Homo during the Middle Pleistocene is controversial, called the "muddle in the middle", owing to the wide anatomical range of variation that populations exhibited during this time. H. heidelbergensis has been regarded as either the last common ancestor of modern humans, Neanderthals, and Denisovans; or as a completely separate lineage.

H. heidelbergensis was described by German anthropologist Otto Schoetensack in 1908 based on a jawbone, Mauer 1, from a sand pit near the village of Mauer — 10 km (6.2 mi) southeast of Heidelberg. It was the oldest identified human fossil in Europe, and Schoetensack described it as an antediluvian race (before the Great Flood) which would eventually evolve into living Europeans. By the mid-20th century, all archaic human taxa were lumped as subspecies of either H. erectus or H. sapiens, with the former evolving into the latter without any coexistence. The species was usually lumped as H. e. heidelbergensis. While its utility was complicated by its definition on a jawbone (which is rarely ever found, and otherwise bears few diagnostic features) British physical anthropologist Chris Stringer revived the species in 1983, redefining it as a Euro-African ancestor of modern humans and Neanderthals using namely Kabwe 1, Petralona 1, Bodo, and Arago. These skulls are united mainly by their supraorbital torus (brow ridge) anatomy.

H. heidelbergensis may have evolved from H. ergaster (African H. erectus) possibly following an intense population bottleneck 800,000 to 900,000 years ago. Populations dispersed into Europe by 700,000 years ago, spreading Late Acheulean stone tools, and settlements became more permanent by 500,000 years ago. H. heidelbergensis may have been an active hunter of big game, including straight-tusked elephant and rhinoceros but at least some populations also subsisted significantly on foodplants and small game. Fire does not seem to have been used frequently, but huts and temporary shelters may have been constructed at least around Europe. There are some instances of nondescript etchings on pebbles, as well as modified and heated ochre, which could have been done with symbolic intentions.

On 21 October 1907, miners recovered a large human mandible (lower jaw) about 24.1 m (79 ft) down the Grafenrain sand pit near the village of Mauer — 10 km (6.2 mi) southeast of Heidelberg. German geologists Ernst Wilhelm Benecke [de] and Adolf Sauer [de] had earlier characterised the site as diluvial deposits (remnants of the Great Flood) dating to the Tertiary. Mauer 1 was the oldest European human fossil at the time. German anthropologist Otto Schoetensack made the first report of the skull in 1908, classifying it as a new human species, Homo heidelbergensis. After Neanderthals (H. neanderthalensis), it was the second-named fossil species in the genus Homo.

Schoetensack noted the jaw's exceptionally primitive anatomy with its massive size and lack of chin, yet more modern traits such as small teeth; reminiscent of the lower races instead of living Europeans. Therefore, he concluded Mauer 1 must represent an ancient European ancestor, which he claimed was further supported by several ontogenetic developments in Europeans. He also claimed that the many similarities with non-human apes indicate that Mauer 1 lies near the last common ancestor of apes and humans. Based on the mammal fauna of the site, he concluded that the jawbone was of antediluvian age (before the Great Flood), but he had failed to find Adam (who he said was the progenitor of all humans, including H. heidelbergensis, but certainly not Aboriginal Australians).

Allerdings sind die Maße groβ [in Mauer 1], wenn man moderne europäische Objekte zum Vergleich heranzieht. Sowie man aber diesen auf jetzige niedere Rassen ausdehnt, verschwindet die Differenz.

The dimensions are large [in Mauer 1] when modern European objects are used for comparison. However, as soon as one extends this to present-day lower races, the difference disappears.

— Otto Schoetensack, 1908