Pharaoh is a title used in many modern discussions of the ancient Egyptian rulers of all periods. In antiquity this title began to be used for the ruler who was the religious and political leader of united ancient Egypt. This was true only during the New Kingdom, specifically during the middle of the eighteenth dynasty. For simplification however, there is a general acceptance amongst modern writers to use the term to relate to all periods.

Pharaoh meaning "Great House", originally referred to the king's palace but by the reign of Thutmose III (ca. 1479-1425 BCE) in the New Kingdom had become a form of address for the person of the king. The Egyptian term for the ruler himself was nsw(t)-bjt(j) (rendered in Babylonian as insibya; Egyptological pronunciation "Nesu(t)-Bit(i)"), "King of Upper and Lower Egypt", literally "he of the sedge and the bee" (properly nj-sw.t-bj.t)), the sedge and the bee being the symbols for Upper and Lower Egypt, respectively. Also nsw.t-t3wj "King of the Two Lands".

This double kingship was expressed in the Pschent, the double crown combining the red crown of Lower Egypt (Deshret) and the white crown of Upper Egypt (Hedjet).

Initially the rulers were considered the sons of the cow deity Bat and eventually Hathor and they occupied her throne to rule the country and officiate in religious rites. There is evidence that the ruler may have been sacrificed after a certain period of time in the earliest rituals but soon was replaced by a specially selected bull. The pharaohs were believed later in the culture to be the incarnations of the deity Horus in life and Osiris in death. Once the cult of Isis and Osiris became prominent, pharaohs were viewed as a bridge between the god Osiris and human beings; and after death the pharaoh was believed to unite with Osiris. The royal line was matriarchal and a relationship with the royal women through birth or marriage (or both) determined the right to rule. The royal women played important roles in the religious rituals and governance of the country, sometimes participating alongside the pharaoh.

The term pharaoh ultimately was derived from a compound word represented as pr-`3, written with the two biliteral hieroglyphs pr "house" and `3 "column". It was used only in larger phrases such as smr pr-`3 'Courtier of the High House', with specific reference to the buildings of the court or palace itself. From the twelfth dynasty onward the word appears in a wish formula 'Great House, may it live, prosper, and be in health', but again only with reference to the royal palace and not the person.

The earliest instance where pr-`3 is used specifically to address the ruler is in a letter to Amenhotep IV (Akhenaten) in the mid-eighteenth dynasty (1550-1292 BC) which is addressed to 'Pharaoh, all life, prosperity, and health!. This may be contrasted with Hatshepsut, who ruled before him in the same eighteenth dynasty, who never had pr-`3 among her titles.

From the nineteenth dynasty onward pr-`3 on its own was used as regularly as hm.f, 'His Majesty'. The term therefore evolved from a word specifically referring to a building to a respectful designation for the ruler, particularly by the twenty-second dynasty and twenty-third dynasty. By this time, the Late Egyptian word is reconstructed to have been pronounced *par-ʕoʔ whence comes Ancient Greek φαραώ pharaō and then Late Latin pharaō. From the latter, English obtained the word "Pharaoh". Over time, *par-ʕoʔ evolved into Sahidic Coptic prro ⲡⲣ̅ⲣⲟ and then rro (by mistaking p- as the definite article prefix "the" from Ancient Egyptian p3).

A similar development, with a word originally denoting an attribute of the ruler eventually coming to refer to the person, can be discerned in a later period with the Arabic term Sultan.

Following unification, the ruler of Egypt wore a double crown, created from the Red Crown of Lower Egypt and the White Crown of Upper Egypt. In certain situations, the pharaoh wore a blue crown of a different shape. Typically, all of these crowns were adorned by a uraeus, which was doubled during the twenty-fifth dynasty.

After the third dynasty, the pharaoh also wore a striped headcloth called the nemes, which may be the most familiar pharaonic headgear. The nemes was sometimes combined with the double crown, as it is on the statues of Ramesses II at Abu Simbel.

The pharaoh often was depicted as wearing a false beard made of goat hair during rituals and ceremonies.

Egyptologist Bob Brier has noted that despite its widespread depiction in royal portraits, no ancient Egyptian crown ever has been discovered. Tutankhamun's tomb, discovered largely intact, did contain such regal items as his crook and flail, but not a crown. It is presumed that crowns would have been believed to have magical properties. Brier's speculation is that there were religious or state items a dead pharaoh could not retain as a personal possession which, therefore, had to be passed along to a successor.