Ralph I of Vermandois was Count of Vermandois. He was a son of Hugh, Count of Vermandois and his wife, Adelaide, Countess of Vermandois. Ralph was a grandson of Henry I of France, while Ralph's mother had been the Carolingian heiress to Herbert IV, Count of Vermandois.

Hugh, called the Great was the first count of Vermandois from the House of Capet. He is known primarily for being one of the leaders of the First Crusade. His nickname Magnus is probably a bad translation into medieval Latin of an Old French nickname, le Maisné, meaning "the younger", referring to Hugh as younger brother of King Philip I of France.