Harold I, also known as Harold Harefoot, was a King of England who reigned from 1035 to 1040. He was the son of Cnut, a Danish king, and Aelgifu of Northumbria. Harold became king after the death of his half-brother, Harthacnut, and ruled primarily over England while his brother was in Denmark. Harold I's reign was marked by conflict and instability, as he faced challenges from rival factions and claims to the throne. His rule ended when he died in 1040, after which Harthacnut returned to England to reclaim the throne, leading to a shift in power dynamics in the region.