Gwladus Ddu, ("Gwladus the Dark"), full name Gwladus ferch Llywelyn (died 1251) was a Welsh noblewoman who was a daughter of Llywelyn the Great of Gwynedd and married two Marcher lords.

Sources differ as to whether Gwladus was Llywelyn's legitimate daughter by his wife Joan or an illegitimate daughter by Tangwystl Goch. Some sources[who?] say that Joan gave her lands to Gwladus, which suggests, but does not prove, the former. Gwladus is recorded in Brut y Tywysogion as having died at Windsor in 1251.

- http://en.wikipedia.org/wiki/Gwladus_Ddu