Guy I of Châtillon, Count of Blois (died 12 August 1342), son of Hugh II of Châtillon and Beatrix of Dampierre, was Count of Blois and Lord of Avesnes 1307–1342.
In 1310, he married Margaret of Valois, daughter of Charles of Valois and sister of Philip VI of France. They had:
Louis II, Count of Blois (d. 1346)
Charles of Blois (d. 1364) - would marry Joanna, Duchess of Brittany; Charles and the French would engage in the Breton War of Succession against the House of Montfort and the English
Marie of Blois, married in 1334 Rudolph, Duke of Lorraine (d. 1346), married secondly Frederick VII, Count of Leiningen-Dagsburg.
Guy took part in the expedition of Louis X of France against Robert III of Flanders in 1315. During the early stages of the Hundred Years' War, he supported the Valois monarchy, to which he was closely connected through his wife, Margaret of Valois.