Gwladus Ddu, ("Gwladus the Dark Eyes"), full name Gwladus ferch Llywelyn (died 1251) was a Welsh noblewoman who was a daughter of Llywelyn the Great of Gwynedd and Joan Plantagenet, a daughter of John, King of England. She married two Marcher lords. Sources differ as to whether Gwladus was Llywelyn's legitimate daughter by his wife Joan or an illegitimate daughter by , but she is widely regarded to be the daughter of Joan. Gwladus is recorded in Brut y Tywysogion as having died at Windsor in 1251.