Arthfael ap Rhys (son of Rhys) was a prince of Glywsing (modern Glamorgan) and Gwent in the late eighth century. He is dated by the genealogist Peter Bartrum to c.760.
His father was called Rhys and his mother was probably Ceingar ferch Maredudd ap Tewdws of Dyfed. His wife was Brawstudd ferch Gloud ap Pasgen Buellt. According to Bartrum, Arthfael had two sons, "Meurig of the line of Gwent" and "Rhys of the line of Glywsing". Two late ninth century brothers had a father called Arthfael. Rhys ap Arthfael was the father of Hywel ap Rhys (died 886), king of Glywsing, and Meurig ap Arthfael was the father of Brochfael ap Meurig and Ffernfael ap Meurig, joint kings of Gwent (fl. 880s). The names and locations suggest that the kings of Glywsing and Gwent were descended from Arthfael ap Rhys. The historian Thomas Charles-Edwards gives Arthfael's father's name as Rhys and says that Meurig may have died in 849, whereas Wendy Davies states that Meurig ap Arthfael ruled until 874 and does not give Arthfael's patronym. The three scholars appear to be discussing the same Arthfael, and the explanation for the discrepancies in dates is unclear.