Isaac ben Judah ibn Ghiyyat (or Ghayyat) (Hebrew: יצחק בן יהודה אבן גיאת, Arabic: ﺇﺑﻦ ﻏﻴﺎث ibn Ghayyath) (1030/1038–1089) was a Spanish rabbi, Biblical commentator, codifier of Jewish law, philosopher, and liturgical poet. He was born and lived in the town of Lucena, where he also headed a rabbinic academy. He died in Cordoba.