Hathor (Ancient Egyptian: ḥwt-ḥr, lit. 'House of Horus', Ancient Greek: Ἁθώρ Hathōr, Coptic: ϩⲁⲑⲱⲣ, Meroitic: 𐦠𐦴𐦫𐦢‎ Atari) was a major goddess in ancient Egyptian religion who played a wide variety of roles. As a sky deity, she was the mother or consort of the sky god Horus and the sun god Ra, both of whom were connected with kingship, and thus she was the symbolic mother of their earthly representatives, the pharaohs. She was one of several goddesses who acted as the Eye of Ra, Ra's feminine counterpart, and in this form, she had a vengeful aspect that protected him from his enemies. Her beneficent side represented beauty, music, dance, joy, love, sexuality, and maternal care, and she acted as the consort of several male deities and the mother of their sons. These two aspects of the goddess exemplified the Egyptian conception of femininity. Hathor crossed boundaries between worlds, helping deceased souls in the transition to the afterlife.

Hathor was often depicted as a cow, symbolizing her maternal and celestial aspect, although her most common form was a woman wearing a headdress of cow horns and a sun disk. She could also be represented as a lioness, a cobra, or a sycomore tree.

Cattle goddesses similar to Hathor were portrayed in Egyptian art in the fourth millennium BC, but she may not have appeared until the Old Kingdom (c. 2686–2181 BC). With the patronage of Old Kingdom rulers, she became one of Egypt's most important deities. More temples were dedicated to her than to any other goddess; her most prominent temple was Dendera in Upper Egypt. She was also worshipped in the temples of her male consorts. The Egyptians connected her with foreign lands, such as Nubia and Canaan, and their valuable goods, such as incense and semiprecious stones, and some of the peoples in those lands adopted her worship. In Egypt, she was one of the deities commonly invoked in private prayers and votive offerings, particularly by women desiring children.

During the New Kingdom (c. 1550–1070 BC), goddesses such as Mut and Isis encroached on Hathor's position in royal ideology, but she remained one of the most widely worshipped deities. After the end of the New Kingdom, Hathor was increasingly overshadowed by Isis, but she continued to be venerated until the extinction of ancient Egyptian religion in the early centuries AD.

Images of cattle appear frequently in the artwork of Predynastic Egypt (before c. 3100 BC), as do images of women with upraised, curved arms, reminiscent of the shape of bovine horns. Both types of imagery may represent goddesses connected with cattle. Cows are venerated in many cultures, including ancient Egypt, as symbols of motherhood and nourishment, because they care for their calves and provide humans with milk. The Gerzeh Palette, a stone palette from the Naqada II period of prehistory (c. 3500–3200 BC), shows the silhouette of a cow's head with inward-curving horns surrounded by stars. The palette suggests that this cow was also linked with the sky, as were several goddesses from later times who were represented in this form: Hathor, Mehet-Weret, and Nut.

Despite these earlier precedents, Hathor is not unambiguously mentioned or depicted until the Fourth Dynasty (c. 2613–2494 BC) of the Old Kingdom, although several artifacts that refer to her may date to the Early Dynastic Period (c. 3100–2686 BC). When Hathor does clearly appear, her horns curve outward, rather than inward like those in Predynastic art.

A bovine deity with inward-curving horns appears on the Narmer Palette from near the start of Egyptian history, both atop the palette and on the belt or apron of the king, Narmer. The Egyptologist Henry George Fischer suggested this deity may be Bat, a goddess who was later depicted with a woman's face and inward-curling horns, seemingly reflecting the curve of the cow horns. The Egyptologist Lana Troy, however, identifies a passage in the Pyramid Texts from the late Old Kingdom that connects Hathor with the "apron" of the king, reminiscent of the goddess on Narmer's garments, and suggests the goddess on the Narmer Palette is Hathor rather than Bat.

In the Fourth Dynasty, Hathor rose rapidly to prominence. She supplanted an early crocodile god who was worshipped at Dendera in Upper Egypt to become Dendera's patron deity, and she increasingly absorbed the cult of Bat in the neighboring region of Hu, so that in the Middle Kingdom (c. 2055–1650 BC) the two deities fused into one. The theology surrounding the pharaoh in the Old Kingdom, unlike that of earlier times, focused heavily on the sun god Ra as king of the gods and father and patron of the earthly king. Hathor ascended with Ra and became his mythological wife, and thus divine mother of the pharaoh.