ancient Greek region and city-state in the northwestern corner of the Peloponnese, well known for its horse breeding and for the Olympic Games, which were allegedly founded there in 776 BC.

The region was bounded on the north by Achaea, on the east by Arcadia, and on the south by Messenia. Elis consisted of three districts from north to south: Hollow Elis, which occupied the basin of the Peneus River; Pisatis, occupying the north bank of the Alpheus River; and Triphylia, a hilly area stretching south from the Alpheus to the northern border of Messenia. Comparatively high rainfall produced good pasture and arable land in low-lying areas, and the region became noted for its horses, cattle, and flax.

The Olympic Games were celebrated every four years at the sanctuary of Olympia, on the north bank of the Alpheus River. The city of Elis, located in Hollow Elis, engaged in a long struggle with the Pisatians for control of the games until 572 BC, when the Eleans decisively subjugated the Pisatians. Having gained control of the entire region by 580, the city of Elis briefly joined Sparta in an anti-Persian alliance (479), then broke with Sparta, adopted a democratic constitution (c. 471), and became the administrative centre of a union of smaller townships. During the Peloponnesian War, Elis again allied with Sparta until 420, when it defected to the side of Athens. Sparta subsequently punished Elis for its defection by stripping it of Triphylia, and Elis's attempts to recover the latter were repeatedly frustrated by Sparta and then by Arcadia. But by adroit diplomacy and by emphasizing the sanctity of the Olympic Games (and the neutrality of Elis as the games' host), the city was able to retain its territory and in some sense even its independence after the Roman occupation of Greece (146 BC), only to disintegrate with the collapse of the Roman Empire.

The modern-day locality contains one of the finest archaeological sites in modern Greece, that of Olympia, scene of the games. The area is now part of Iliá nomos (department), and its principal towns are Pyrgos and Amalias.