Hugh of Vermandois (1053 - October 18, 1101), was the brother of King Philip I of France, and count of Vermandois. He married Adela (Adelheid) daughter of Hebert IV Count of Valois and Adela de Vexin. William of Tyre called him "Hugh Magnus", Hugh the Great, but he was an ineffectual leader and soldier, great only in his boasting.

In early 1096 Hugh and Philip began discussing the First Crusade after news of the Council of Clermont reached them in Paris. Although Philip could not participate, as he had been excommunicated, Hugh was said to have been influenced to join the Crusade after an eclipse of the moon on February 11, 1096.

That summer Hugh's army left France for Italy, where they would cross the Adriatic Sea into territory of the Byzantine Empire, unlike the other Crusader armies who were travelling by land. On the way, many of the soldiers led by fellow Crusader Emich of Leiningen joined Hugh's army after Emich was defeated by the Hungarians, whose land he had been pillaging. Hugh crossed the Adriatic from Bari in southern Italy, but many of his ships were destroyed in a storm off the Byzantine port of Dyrrhachium. Hugh and most of his army was rescued and escorted to Constantinople, where they arrived in November of 1096. Prior to his arrival, Hugh sent an arrogant, insulting letter to Emperor Alexius I, demanding that Alexius meet with him: "Know, O King, that I am King of Kings, and superior to all, who are under the sky. You are now permitted to greet me, on my arrival, and to receive me with magnificence, as befits my nobility." Alexius was already wary of the armies about to arrive, after the unruly mob led by Peter the Hermit had passed through earlier in the year. Alexius kept Hugh in custody in a monastery until Hugh swore an oath of vassalage to him.

After the Crusaders had successfully made their way across Seljuk territory and, in 1098, captured Antioch, Hugh was sent back to Constantinople to appeal for reinforcements from Alexius. Alexius was uninterested, however, and Hugh, instead of returning to Antioch to help plan the siege of Jerusalem, went back to France. There he was scorned for not having fulfilled his vow as a Crusader to complete a pilgrimage to Jerusalem, and Pope Paschal II threated to excommunicate him. He joined the minor Crusade of 1101, but was wounded in battle with the Turks at Heraclea in June, and died of his wounds in October in Tarsus.