Gruffydd ap Llywelyn (c. 1007–1063 or 1064) is the ruler of all Wales from 1055 until his death.

He is the usurped son of King Llywelyn ap Seisyll and should not be confused with the dispossessed son of the later Prince Llywelyn the Great.

Although the true lineage of his grandfather Seisyll is obscure, he claims to be a the great-great-grandson of Hywel Dda.