Rhys Mechyll (died 1244) was a Welsh prince, Lord of Dinefwr, of the House of Dinefwr and Kingdom of Deheubarth in southern Wales from 1234 to 1244. He was a son of prince Rhys Gryg (died 1234) ("Rhys the Hoarse"), son of prince Rhys ap Gruffydd (1132–1197),[1] "The Lord Rhys", ruler of the kingdom of Deheubarth.