Horus (/hɔːrəs/), also known as Heru, Har, Her, or Hor (/hɔːr/) Ϩⲱⲣ (Coptic), in Ancient Egyptian, is one of the most significant ancient Egyptian deities who served many functions, most notably as the god of kingship, healing, protection, the sun, and the sky. He was worshipped from at least the late prehistoric Egypt until the Ptolemaic Kingdom and Roman Egypt. Different forms of Horus are recorded in history, and these are treated as distinct gods by Egyptologists. These various forms may be different manifestations of the same multi-layered deity in which certain attributes or syncretic relationships are emphasized, not necessarily in opposition but complementary to one another, consistent with how the Ancient Egyptians viewed the multiple facets of reality. He was most often depicted as a falcon, most likely a lanner falcon or peregrine falcon, or as a man with a falcon head.

The earliest recorded form of Horus is the tutelary deity of Nekhen in Upper Egypt, who is the first known national god, specifically related to the ruling pharaoh who in time came to be regarded as a manifestation of Horus in life and Osiris in death. The most commonly encountered family relationship describes Horus as the son of Isis and Osiris, and he plays a key role in the Osiris myth as Osiris's heir and the rival to Set, the murderer and brother of Osiris. In another tradition, Hathor is regarded as his mother and sometimes as his wife.

Practicing interpretatio romana, Claudius Aelianus wrote that Egyptians called the god Apollo "Horus" in their own language. However, Plutarch, elaborating further on the same tradition reported by the Greeks, specified that the one "Horus" whom the Egyptians equated with the Greek Apollo was in fact "Horus the Elder", a primordial form of Horus whom Plutarch distinguishes from both Horus and Harpocrates.

Horus is recorded in Egyptian hieroglyphs as ḥr.w "Falcon", 𓅃; the original pronunciation has been reconstructed as /ˈħaːɾuw/ in Old Egyptian and early Middle Egyptian, /ˈħaːɾəʔ/ in later Middle Egyptian, and /ˈħoːɾ(ə)/ in Late Egyptian. Additional meanings are thought to have been "the distant one" or "one who is above, over". As the language changed over time, it appeared in Coptic varieties variously as /hɔr/ or /ħoːɾ/ (Ϩⲱⲣ) and was adopted into ancient Greek as Ὧρος Hō̂ros (pronounced at the time as /hɔ̂ːros/). It also survives in Late Egyptian and Coptic theophoric name forms such as Siese "son of Isis" and Harsiese "Horus, Son of Isis".

Horakhti or Hor-Akhti, "Horus of the Two Horizons", was the personification of the Sun on the horizon according to Egyptian mythology.

The pharaoh was associated with many specific deities. He was identified directly with Horus, who represented kingship itself and was seen as a protector of the pharaoh, and he was seen as the son of Ra, who ruled and regulated nature as the pharaoh ruled and regulated society.

The Pyramid Texts (c. 2400–2300 BCE) describe the nature of the pharaoh in different characters as both Horus and Osiris. The pharaoh as Horus in life became the pharaoh as Osiris in death, where he was united with the other gods. New incarnations of Horus succeeded the deceased pharaoh on earth in the form of new pharaohs.

The lineage of Horus, the eventual product of unions between the children of Atum, may have been a means to explain and justify pharaonic power. The gods produced by Atum were all representative of cosmic and terrestrial forces in Egyptian life. By identifying Horus as the offspring of these forces, then identifying him with Atum himself, and finally identifying the Pharaoh with Horus, the Pharaoh theologically had dominion over all the world.