The Neanderthal (IPA: /ne??ænd?rt??l/, also with /ni?-/ and /-???l/), or Neandertal, is an extinct member of the Homo genus that is known from Pleistocene specimens found in Europe and parts of western and central Asia. Neanderthals are either classified as a subspecies of humans (Homo sapiens neanderthalensis) or as a separate species (Homo neanderthalensis). The first proto-Neanderthal traits appeared in Europe as early as 600,000–350,000 years ago. Proto-Neanderthal traits are occasionally grouped to another cladistic 'species', Homo heidelbergensis, or a migrant form, Homo rhodesiensis. By 130,000 years ago, complete Neanderthal characteristics had appeared. These characteristics then disappeared in Asia by 50,000 years ago and in Europe by 30,000 years ago. The youngest Neanderthal finds include Hyaena Den (UK), considered older than 30,000 years ago, while the Vindija (Croatia) Neanderthals have been re-dated to between 32,000 and 33,000 years ago. No definite specimens younger than 30,000 years ago have been found; however, evidence of fire by Neanderthals at Gibraltar indicate that they may have survived there until 24,000 years ago. Modern human skeletal remains with 'Neanderthal traits' were found in Lagar Velho (Portugal), dated to 24,500 years ago and interpreted as indications of extensively admixed populations.

Neanderthal stone tools provide further evidence for their presence where skeletal remains have not been found. The last traces of Mousterian culture, a type of stone tools associated with Neanderthals, were found in Gorham's Cave on the remote south-facing coast of Gibraltar. Other tool cultures sometimes associated with Neanderthal include Châtelperronian, Aurignacian, and Gravettian, with the latter extending to 22,000 years ago, the last indication of Neanderthal presence.

Neanderthal cranial capacity is often thought to have been as large or larger than modern humans, indicating that their brain size may have been the same or greater; however, a 1993 analysis of 118 hominid crania concluded that the cranial capacity of H.s. neandertal averaged 1412cc while that of fossil modern H.s. sapiens averaged 1487cc. They were almost exclusively carnivorous and apex predators. On average, the height of Neanderthals was comparable to contemporaneous Homo sapiens. Neanderthal males stood about 165–168 cm tall (about 5'5") and were heavily built with robust bone structure. They were much stronger, having particularly strong arms and hands. Females stood about 152–156 cm tall (about 5'1").