In the Book of Genesis, Hagar (הגר "Stranger", Standard Hebrew Hagar, Tiberian Hebrew Hāḡār; Arabic Hajar) is an Egyptian-born servant of Sarah, wife of Abraham.

Hagar is the Egyptian slave of Abraham and Sarah, mentioned in Genesis 16. As was the custom, the childless Sarah offered Hagar to her husband Abraham to provide him with an heir. The son born from this union was Ishmael.

The text avoids praise of these actions, and traditional readings often hold that this ignored God's promise to provide Abraham with an heir through Sarah herself. When this promise was fulfilled in the birth of Isaac, Ishmael's behavior was deemed unacceptable, and so Hagar and Ishmael were expelled from the camp of Abraham. This continues a theme of younger sons supplanting older ones that is found through out Torah.

Ishmael is held by tradition to be the father of the Arab people, and a ancestor of Muhammed.

Contemporary readings often discuss the tension between women that is induced by linking women's status to the male heirs they produce. Hagar is often used as example of the silently victimized, since her only recorded statement is a plea for death. Later Liberation and Womanist traditions find identity with Hagar for these reasons.