Akhenaten (pronounced ˌækəˈnɑːtən), also spelled Akhenaton or Echnaton (ꜣḫ-n-jtn ʾŪḫə-nə-yātəy, ˈʔuːχəʔ nə ˈjaːtəj, meaning "Effective for the Aten"), was an ancient Egyptian pharaoh reigning 1353–1336 or 1351–1334 BC, the tenth ruler of the Eighteenth Dynasty. Before the fifth year of his reign, he was known as Amenhotep IV (jmn-ḥtp, meaning "Amun is satisfied", Hellenized as Amenophis IV).
As a pharaoh, Akhenaten is noted for abandoning Egypt's traditional polytheism and introducing Atenism, or worship centered around Aten. The views of Egyptologists differ as to whether the religious policy was absolutely monotheistic, or whether it was monolatristic, syncretistic, or henotheistic. This culture shift away from traditional religion was reversed after his death. Akhenaten's monuments were dismantled and hidden, his statues were destroyed, and his name excluded from lists of rulers compiled by later pharaohs. Traditional religious practice was gradually restored, notably under his close successor Tutankhamun, who changed his name from Tutankhaten early in his reign. When some dozen years later, rulers without clear rights of succession from the Eighteenth Dynasty founded a new dynasty, they discredited Akhenaten and his immediate successors and referred to Akhenaten as "the enemy" or "that criminal" in archival records.
Akhenaten was all but lost to history until the late-19th-century discovery of Amarna, or Akhetaten, the new capital city he built for the worship of Aten. Furthermore, in 1907, a mummy that could be Akhenaten's was unearthed from the tomb KV55 in the Valley of the Kings by Edward R. Ayrton. Genetic testing has determined that the man buried in KV55 was Tutankhamun's father, but its identification as Akhenaten has since been questioned.
Akhenaten's rediscovery and Flinders Petrie's early excavations at Amarna sparked great public interest in the pharaoh and his queen Nefertiti. He has been described as "enigmatic", "mysterious", "revolutionary", "the greatest idealist of the world", and "the first individual in history", but also as a "heretic", "fanatic", "possibly insane", and "mad".