A hand axe is a prehistoric stone tool with two faces that is the longest-used tool in human history. It is made from stone, usually flint or chert that has been "reduced" and shaped from a larger piece by knapping, or hitting against another stone. They are characteristic of the lower Acheulean and middle Palaeolithic (Mousterian) periods, roughly 1.6 million years ago to about 100,000 years ago, and used by Homo erectus and other early humans, but rarely by Homo sapiens.

The Mousterian is an archaeological industry of stone tools, associated primarily with the Neanderthals in Europe, and to the earliest anatomically modern humans in North Africa and West Asia. The Mousterian largely defines the latter part of the Middle Paleolithic, the middle of the West Eurasian Old Stone Age. It lasted roughly from 160,000 to 40,000 BP. If its predecessor, known as Levallois or Levallois-Mousterian, is included, the range is extended to as early as c. 300,000–200,000 BP. The main following period is the Aurignacian of Homo sapiens.