Owain Brogyntyn ap Madog (fl. 1186) was the youngest and illegitimate son of king Madog ap Maredudd, the last king of a united kingdom of Powys. He was the son of Madog by the daughter of the Maer du or "black mayor" of Rûg in Edeyrnion. He was the brother of Gruffydd Maelor the ancestor of Owain Glyndŵr. Presumably Owain Brogyntyn would have been raised by his mother at Rûg in Edeyrnion. He was acknowledged by his father and granted by him the lordship of Edeyrnion and also Dinmael. It is quite possible that he inherited some of these lands through his maternal grandfather, the Maer Du, which were confirmed and perhaps extended by his father the king of Powys. At some point he also came into possession of Castle Brogyntyn on the English borders at Selattyn close to Oswestry.
Owain first married Jonet verch Hywel (whose ancestor was Athelstan Glodrudd of the Fifth Royal Tribe) but with her had no children. He next married Marred ferch Einion ap Seisyllt who was to be the mother of his three sons.
His youngest son, Iorwerth ab Owain Brogyntyn, married Efa verch Madoc the sole heir of Madoc, Lord of Mawddwy (the younger son of Gwenwynwyn, prince of Powys Wenwynwyn). The son of Iorwerth and Efa, Gruffudd ab Iorwerth, was confirmed in his lands as Baron of Edeyrnion by Edward I under the terms of the Statute of Rhuddlan by which England organised the subjugation of Wales.
According to Philip York writing in 1799 a cup and a dagger belonging to Owain Brogyntyn were preserved at Rûg in Edeyrnion. Later accounts in the National Gazetteer dated 1868 state that a cup and dagger in the possession of "Colonel Vaughan of Rhug" were once owned by another Owain of Powys, the much later Owain Glyndŵr. These objects, whoever the original owner, may now be lost.
- York, Philip The Royal Tribes of Wales 1799, p. 119,120