Llefelys (Middle Welsh orthography Llevelys, Lleuelys, Llefelis) is a character in Welsh mythology appearing in the medieval Welsh tale Cyfranc Lludd a Llefelys. In the tale, Llefelys is king of Gaul while his brother Lludd is king of Britain. The tale appears in the Red Book of Hergest and the White Book of Rhydderch, the source texts for the Mabinogion, and embedded into various versions of the Brut y Brenhinedd, the Welsh adaptation of Geoffrey of Monmouth's Historia Regum Britanniae.