Akhenaten (/ˌækəˈnɑːtən/; also spelled Echnaton, Akhenaton,Ikhnaton, and Khuenaten; meaning "Effective for Aten"), known before the fifth year of his reign as Amenhotep IV (sometimes given its Greek form, Amenophis IV, and meaning "Amun Is Satisfied"), was an ancient Egyptian pharaoh of the 18th Dynasty who ruled for years and died perhaps in 1336 BC or 1334 BC. He is noted for abandoning traditional Egyptian polytheism and introducing worship centered on the Aten, which is sometimes described as monolatristic, henotheistic, or even quasi-monotheistic. An early inscription likens the Aten to the sun as compared to stars, and later official language avoids calling the Aten a god, giving the solar deity a status above mere gods.

Akhenaten tried to shift his culture from Egypt's traditional religion, but the shifts were not widely accepted. After his death, his monuments were dismantled and hidden, his statues were destroyed, and his name excluded from the king lists. Traditional religious practice was gradually restored, and when some dozen years later rulers without clear rights of succession from the 18th Dynasty founded a new dynasty, they discredited Akhenaten and his immediate successors, referring to Akhenaten himself as "the enemy" or "that criminal" in archival records.

He was all but lost from history until the discovery during the 19th century of the site of Akhetaten, the city he built and designed for the worship of Aten, at Amarna. Early excavations at Amarna by Flinders Petrie sparked interest in the enigmatic pharaoh, and a mummy found in the tomb KV55, which was unearthed in 1907 in a dig led by Edward R. Ayrton, is likely that of Akhenaten. DNA analysis has determined that the man buried in KV55 is the father of King Tutankhamun, but its identification as Akhenaten has been questioned.