In the Old Testament, Basemath (spelled Bashemath or Basmath in the KJV) is the name of three women.
In Genesis 26:34 Basemath is the daughter of Elon the Hittite, and one of the three wives of Esau. In Genesis 36:2 she is called Adah, and is the only one of Esau's wives of whom his father Isaac approved, as the other two were both Canaanites.
In Genesis 36:3-4,10,13,17 Basemath is the daughter of Ishmael and another of the three wives of Esau. In Genesis 28:9 she is called Mahalath.