The aurochs (Bos primigenius) ( or ) is an extinct cattle species, considered to be the wild ancestor of modern domestic cattle. With a shoulder height of up to 180 cm (71 in) in bulls and 155 cm (61 in) in cows, it was one of the largest herbivores in the Holocene; it had massive elongated and broad horns that reached 80 cm (31 in) in length.

The aurochs was part of the Pleistocene megafauna. It probably evolved in Asia and migrated west and north during warm interglacial periods. The oldest known aurochs fossils found in India and North Africa date to the Middle Pleistocene and in Europe to the Holstein interglacial. As indicated by fossil remains in Northern Europe, it reached Denmark and southern Sweden during the Holocene. The aurochs declined during the late Holocene due to habitat loss and hunting, and became extinct when the last individual died in 1627 in Jaktorów forest in Poland.

The aurochs is depicted in Paleolithic cave paintings, Neolithic petroglyphs, Ancient Egyptian reliefs and Bronze Age figurines. It symbolised power, sexual potency and prowess in religions of the ancient Near East. Its horns were used in votive offerings, as trophies and drinking horns.

Two aurochs domestication events occurred during the Neolithic Revolution. One gave rise to the domestic cattle (Bos taurus) in the Fertile Crescent in the Near East that was introduced to Europe via the Balkans and the coast of the Mediterranean Sea. Hybridisation between aurochs and early domestic cattle occurred during the early Holocene. Domestication of the Indian aurochs led to the zebu cattle (Bos indicus) that hybridised with early taurine cattle in the Near East about 4,000 years ago. Some modern cattle breeds exhibit features reminiscent of the aurochs, such as the dark colour and light eel stripe along the back of bulls, the lighter colour of cows, or an aurochs-like horn shape.