The eldest son of William the Conqueror, succeding him as Duke of Normandy (1087), but not on the English throne. Robert Curthose (so called for his short squat appearance), was renowned for his homosexual and orgiastic gatherings (power again, you see) and William abhorred this behaviour (even though homosexuality was quite commonplace and tolerated at the time). Aided by King Philip I of France, he rebelled (1077) against his father. Father and son became reconciled, but Robert was later exiled.

At William's death he inherited Normandy. England fell to his younger brother William II (who was also gay), with whom Robert was intermittently at war (1090-96) until Robert went (1096-1100) on the First Crusade. While he was away, William II died and Henry I, youngest son of William I, was crowned.

Robert invaded (1101) England but was forced to recognize Henry. In Normandy, Robert's misgovernment prompted an invasion by Henry (1105), who defeated (1106) Robert at Tinchebrai, seized Normandy, and kept Robert a prisoner in England, in the Cardiff castle, South Glamorgan, Wales, till his death. He is buried in Cloucester Cathedral, Gloucestershire.