In the Book of Genesis, Zilpah (זִלְפָּה "drooping", Standard Hebrew Zilpa, Tiberian Hebrew Zilpâ) was Leah's handmaid, who Leah gave to Jacob "to wife" to bear him children. (Genesis 30:9) Zilpah gave birth to two sons, who Leah claimed as her own and named Gad and Asher. (Genesis 30:10-13) (The prefix "to", as in "took to wife", may indicate that the wife is a concubine or inferior wife.)
Zilpah is given to Leah as a handmaid by Leah's father, Laban, upon Leah's marriage to Jacob (see Genesis 29:24, 46:18). According to some commentators, Zilpah and Bilhah, the handmaids of Leah and Rachel, respectively, were actually younger daughters of Laban. (Pirke De-Rabbi Eliezer, xxxvi.)
Zilpah also figures in the competition between Jacob's wives to bear him sons. Leah stops conceiving after the birth of her fourth son, at which point Rachel, who had not yet borne children, offers her handmaid, Bilhah, "to wife" to Jacob so that she can have children through her. When Bilhah conceives two sons, Leah takes up the same idea and presents Zilpah "to wife" to Jacob. Leah names the two sons of Zilpah and is directly involved in their upbringing.