Gruffydd ap Rhys II (died 25 July 1201) was a prince of Deheubarth in south-west Wales.
But Maelgwn used troops supplied by Gwenwynwyn ab Owain of Powys to attack Aberystwyth.
In 1198 Gwenwynwyn threatened the English holdings at Painscastle and Elfael, and Gruffydd was released from captivity to try to mediate in the dispute.
Gruffydd retained his liberty and by the end of the year had captured all of Ceredigion from Maelgwn except for the castles of Cardigan and Ystrad Meurig.
Maelgwn made an agreement with King John of England, selling Cardigan castle to him in exchange for the possession of the remainder of Ceredigion.