Robert the Strong, d. 866, French warrior, marquess of Neustria; father of the French kings Eudes and Robert I and ancestor of the Capetians. He joined the rebellious nobles against Charles II, Emperor of the West. They invited Louis the German to invade France (858). Becoming reconciled to Charles in 861, Robert was charged with the defense of the country between the Seine and the Loire, from which he repelled the Bretons and the Normans. He was killed fighting against the Normans.