oswiu (–15 february 670), also known as oswy or , became the king of bernicia at the death of his brother oswald. later he became the king of northumbria. when oswiu defeated and killed penda of mercia at the battle of the winwaed, he became the seventh over the southern english kings. he took the throne of mercia and appointed his son-in-law peada (penda's son) as a client king. oswiu was one of those rare kings of northumbria who died of natural causes and not in battle.