Athelred I (675–716) was the third of Penda's sons to be king of Mercia. He ravaged Kent to prevent them from breaking away from his rule. In 679 he was at war with Northumbria. According to Bede, Theodore Archbishop of Canterbury between the two kings to restore peace. He married Ostryth, daughter of the king of Bernicia. He was a Christian king who founded several churches and monasteries. He stepped down as king in 704 and passed the crown to his nephew Cenred. He was of the monastery of Bardsey and appears to have died about 716.