The Kurgan hypothesis (also theory or model) is one of the proposals about early Indo-European origins, which postulates that the people of an archaeological "Kurgan culture" (a term grouping the Yamna, or Pit Grave, culture and its predecessors) in the Pontic steppe were the most likely speakers of the Proto-Indo-European language. The term is derived from kurgan (курган), a Turkic loanword in Russian for a tumulus or burial mound.
The Kurgan model is the most widely accepted scenario of Indo-European origins. An alternative model is the Anatolian urheimat. Many Indo-Europeanists are agnostic on the question.
The Kurgan hypothesis was first formulated in the 1950s by Marija Gimbutas, who defined the "Kurgan culture" as composed of four successive periods, with the earliest (Kurgan I) including the Samara and Seroglazovo cultures of the Dnieper/Volga region in the Copper Age (early 4th millennium BC). The bearers of these cultures were nomadic pastoralists, who, according to the model, by the early 3rd millennium BC expanded throughout the Pontic-Caspian steppe and into Eastern Europe.
When it was first proposed in 1956, in "The Prehistory of Eastern Europe, Part 1", Marija Gimbutas's contribution to the search for Indo-European origins was a pioneering interdisciplinary synthesis of archaeology and linguistics. The Kurgan model of Indo-European origins identifies the Pontic-Caspian steppe as the Proto-Indo-European (PIE) Urheimat, and a variety of late PIE dialects are assumed to have been spoken across the region. According to this model, the Kurgan culture gradually expanded until it encompassed the entire Pontic-Caspian steppe, Kurgan IV being identified with the Pit Grave culture of around 3000 BC.
The mobility of the Kurgan culture facilitated its expansion over the entire Pit Grave region, and is attributed to the domestication of the horse and later the use of early chariots. The first strong archaeological evidence for the domestication of the horse comes from the Sredny Stog culture north of the Azov Sea in Ukraine, and would correspond to an early PIE or pre-PIE nucleus of the 5th millennium BC. The earliest known chariot was discovered at Krivoye Lake and dates to c. 2000 BC.
Subsequent expansion beyond the steppes led to hybrid, or in Gimbutas's terms "kurganized" cultures, such as the Globular Amphora culture to the west. From these kurganized cultures came the immigration of proto-Greeks to the Balkans and the nomadic Indo-Iranian cultures to the east around 2500 BC.
J.P. Mallory’s inconclusiveness about the westward Indo-European migrations was cited by linguist Kortlandt, to conclude that archaeological evidence is pointless beyond what can be motivated from a linguistic point of view. From the 1990s on, new archaeological evidence from Northern European prehistoric cultures resulted in new questions concerning the influence and expansion of Kurgan cultures to the west. The pan-European migrations and process of "kurganization", especially of Corded Ware cultures, may not have been as extensive as Gimbutas believed.
The model of a "Kurgan culture" postulates cultural similarity between the various cultures of the Chalcolithic to Early Bronze Age (5th to 3rd millennia BC) Pontic-Caspian steppe to justify the identification as a single archaeological culture or cultural horizon. The eponymous construction of kurgans is only one among several factors.