Æthelred of Mercia was a seventh-century Anglo-Saxon monarch who ruled the kingdom of Mercia from 675 until 704. As the son of Penda, he ascended the throne following the death of his brother, Wulfhere. His reign was marked by significant military actions, including a victory at the Battle of the Trent, which secured the territory of Lindsey for his kingdom. Known for his deep religious devotion, he supported the church through land grants and provided refuge to exiled clergy, eventually transitioning from a powerful ruler to a monk.