Gruffydd ap Gwenwynwyn (died c. 1286) was a Welsh king who was lord of the part of Powys known as Powys Wenwynwyn and sided with Edward I in his conquest of Wales of 1277 to 1283. Gruffydd was the son of Gwenwynwyn and Margaret Corbet. He was still a child when his father, who had been driven out of his princedom by Llywelyn the Great, died in exile in 1216. He spent his youth in England, maintained by the king, and did not return to Wales until after Llywelyn's death. When Dafydd ap Llywelyn was forced to come to terms with King Henry III of England in 1241, Gruffydd was given most of the lands formerly held by his father, paying homage to Henry for them. Around this time he married Hawise, daughter of John Lestrange of Knockin.