| Guy I of Luxembourg-Ligny | |
| Noble Family: | Luxembourg |
| Father: | John I of Luxembourg, Lord of Ligny |
| Mother: | Alix of Dampierre |
| Spouse: | Mahaut of Châtillon |
| Birth Date: | 1340 |
| Death Place: | Baesweiler |
Guy I of Luxembourg-Ligny (1340 – 23 August 1371) was Count of Saint-Pol (1360–1371) and Count of Ligny, Lord of Roussy and Beauvoir (1364–1371).
He was the son of John I and Alix of Dampierre, dame de Richebourg.
Guy participated in the Battle of Baesweiler (present-day Germany), a conflict between his relative Wenceslaus I of Luxembourg, husband of the Duchess of Brabant on the one side, and William II, Duke of Jülich and Edward, Duke of Guelders on the other side. Guy was killed during the battle.
According to the chronicler Jan van Boendale who wrote in the Brabantsche Yeesten, Guy lay wounded and abandoned on the battlefield, until he was discovered by a scavenger the next day, who killed and robbed him. When this plunderer tried later to sell his booty, he was hanged.
In 1354, Guy married Mahaut de Châtillon (1335–1378), Countess of Saint-Pol, daughter of Jean de Châtillon-Saint-Pol and Jeanne de Fiennes, and had: