Llywelyn or ap Llywelyn is a surname, and may refer to:
Angharad ferch Llywelyn (fl.1260), daughter of Llywelyn ab Iorwerth, Prince of Wales Carmen Llywelyn, American actress and photographer Dafydd ap Llywelyn (1212–1246), King of Gwynedd Dafydd ap Llywelyn ap Madog, Welsh poet of the 16th-century Dafydd Llywelyn (composer) (1939–2013), Welsh pianist and composer Dafydd Llywelyn (politician) (born 1976), Welsh politician Desmond Llewelyn (1914–1999), Welsh actor Elen ferch Llywelyn (c. 1207–1253), daughter of Llywelyn the Great of Gwynedd Emyr Llywelyn, Welsh political activist Llywarch ap Llywelyn (fl.1173–1220), Welsh poet Madog ap Llywelyn (died after 1312), leader of the Welsh revolt of 1294–95 Maredudd ap Llywelyn ap Maredudd ap Cynan, Welsh prince of the 13th century Morgan Llywelyn (born 1937), American-Irish author Owain ap Llywelyn ab y Moel (fl.1470–1500), Welsh poet from Powys Robin Llywelyn (born 1958), Welsh novelist
See also Llywelyn (name) Llewellyn (surname) Llewelyn (surname) Lewellen (surname)