William the Conqueror
Sometimes known as William the Bastard, having been born the illegitimate son of the Duke of Normandy. William inherited the Duchy upon his father's death, but is best known for successfully leading the Norman conquest of England.
William first attempted to gain England through diplomatic maneuvering. He first claimed that Edward the Confessor had named him successor in 1051, and then in 1064 he convinced Harold Godwinson to swear fealty to him and relinquish his claim to the throne. The latter event almost certainly took place under duress, and the former may not have happened at all, but he used both as a pretext for invasion when the witan declared Harold king in January 1066, and the Pope in Rome declared him the rightful King.
William delayed his assault until late September, waiting for favorable winds. All this stretched Harold's resources, as not only did he need to stay on high military alert for several months, but he also had to fight and defeat Harald Hardrada at the demanding Battle of Stamford Bridge.
William's victory at the Battle of Hastings marked a turning point in English history. Not only was it the most successful invasion of Britain by a foreign force, it also marked the beginning of a new dynasty. All kings of England number themselves from the ascension of the Norman kings.
Having been crowned in 1066, William set about securing his new kingdom. Uprisings were brutally quelled, Norman lords were installed into places of power, and by 1072 the whole of England had been united once more.
William's burial was less than dignified. It took several days during an unusually warm September to move his body to his burial site in Caen, Normandy. By the time he was being placed in the sarcophagus, the corpse had swollen to the point that it would not fit. When an attempt was made to force it, William's corpse burst and a great stench poured out, causing his mourners to flee the chapel.