In the Book of Genesis, Hagar (Hajar) is an Egyptian-born servant of Sarah, wife of Abraham.
Her main significance in the story is as the mother of Ishmael. As was the custom, the childless Sarah offered Hagar to her husband Abraham to provide him with an heir. This was ignoring God's promise to provide Abraham with an heir through Sarah herself.
When this promise was fulfilled in the birth of Isaac, Hagar's position became extremely dangerous, and she took Ishmael and fled.
Hagar the Horrible is a comic strip by Dik Browne; the strip is about a Viking.