William I of Namur

William I (1324–1391), called the Rich, ruled Namur from 1337. The fifth son of John I and Marie of Artois, he inherited after four elder brothers died childless, his mother acting as regent.

He joined the English side in the Hundred Years' War, though Namur saw only a weavers' revolt in 1351. With money from his mother and wife he bought more lands and promoted mining, metalworking and trade. In 1362 Emperor Charles IV made Namur directly subject to the Empire, ending its vassalage to Hainaut, and in 1371 William was captured at Baesweiler.

His first wife Jeanne of Hainault died of the plague two years after their wedding; in 1352 he married Catherine of Savoy, mother of William II and John III, the last Marquis of Namur.