Iorwerth mab Owain Gwynedd (or Iorwerth Drwyndwn meaning "the flat-nosed"), also called Edward (c. 1130–1174), was the eldest legitimate son of Owain Gwynedd (the king of Gwynedd) and his first wife Gwladys (Gladys) ferch Llywarch. He married Marared ferch Madog. His son, Llywelyn the Great, eventually united the realm and became known as Llywelyn Fawr and is one of Wales's most famous monarchs. Iorwerth received Nant Conwy as his inheritance from his father, Owain Gwynedd. However, he did not receive the crown succession, as was the normal tradition, because of his nose defect (his sobriquet 'Trwyndwn' means broken-nosed).
- Lloyd, J. E. (1959). The Dictionary of Welsh biography down to 1940. Blackwell (hardcopy).
- Matthew, H. C. G. (23 September 2004). Oxford Dictionary of National Biography: In Association with the British Academy (V31 p.399). OUP Oxford. ISBN 978-0-19-861411-1.