William II, marquis of Namur (22 January 1355 – 10 January 1418) inherited the marquisate of Namur from his father William I in 1391 and held it until his own death.
His mother was Catherine of Savoy († 1388), daughter of Louis II of Savoy, baron of Vaud, and Isabella of Châlon. His rule as marquis was a peaceful one, in which he devoted himself to encouraging commerce, industry and the building of fortifications.
His first wife was Marie de Bar, daughter of Robert I, Duke of Bar and Marie of Valois (1344-1404).
In 1393, he remarried with Jeanne d'Harcourt (1372-1456), daughter of John VI, Count of Harcourt and Catherine of Bourbon.
He had no surviving children and so on his death William II was succeeded as Marquis by his brother John III.
| Preceded by William I |
Marquis of Namur 1391–1418 |
Succeeded by John III |