Llywelyn or Llewelyn ap Iorwerth (hləwĕlˈĭn äp yôrˈwĕrth, lōĕlˈĭn ) [key] (Llywelyn the Great), 1173–1240, Welsh prince; grandson of Owain Gwynedd. He first proved his capacity by wresting (1194) N Wales from his uncle David I and by taking (1199) the border fortress of Mold from the English. He was at first on good terms with King John of England (whose illegitimate daughter Joan he married in 1206), but after 1210 he was attacked by the English king. He became a powerful ally of the English barons in their revolt against John, and his rights and those of the Welsh were recognized in the Magna Carta (1215). Thereafter he set about establishing his power and destroying Norman castles in S Wales. Though he did homage (1218) to John's successor, Henry III, Llywelyn continued fighting against the English until 1234. Llywelyn's munificent patronage of the bards brought a renaissance of Welsh letters. He was an able soldier, a generous supporter of the church, and, above all, a zealous fighter for national unity. He was succeeded by his son David II.