The Proto-Indo-Europeans are a hypothetical prehistoric population of Eurasia who spoke Proto-Indo-European (PIE), the ancestor of the Indo-European languages according to linguistic reconstruction.

Knowledge of them comes chiefly from that linguistic reconstruction, along with material evidence from archaeology and archaeogenetics. The Proto-Indo-Europeans likely lived during the late Neolithic, or roughly the 4th millennium BC. Mainstream scholarship places them in the Pontic–Caspian steppe zone in Eastern Europe (present day Ukraine and southern Russia).[1][2] Some archaeologists would extend the time depth of PIE to the middle Neolithic (5500 to 4500 BC) or even the early Neolithic (7500 to 5500 BC), and suggest alternative location hypotheses.

By the early second millennium BC, descendants of the Proto-Indo-Europeans had reached far and wide across Eurasia, including Anatolia (Hittites), the Aegean (the ancestors of Mycenaean Greece), the north of Europe (Corded Ware culture), the edges of Central Asia (Yamnaya culture), and southern Siberia (Afanasievo culture).[3]