William I, also known as William the Conqueror, was the first Norman King of England, reigning from 1066 until his death in 1087. He was born in 1028 in Falaise, Normandy and became Duke of Normandy in 1035. His claim to the English throne led to the Norman Conquest after he defeated King Harold II at the Battle of Hastings in 1066. William's reign marked significant changes in England, including the introduction of Norman culture and the feudal system. He commissioned the Domesday Book, a comprehensive survey of his new kingdom, which provided valuable information about land ownership and resources.