CHARLEROI (CAROLUS REx), a town in the province of Hainaut, Belgium. Pop. (193o) 28,640. It was founded in 1666 on the site of a village called Charnoy, by the Spanish governor Roderigo, and named after his sovereign Charles II. of Spain. Charleroi is the centre of the chief coalfield of Belgium, with im portant metallurgical and glass industries. It is connected by canal with Brussels, and from its position on the Sambre communicates by water with France. It was ceded soon after its foundation to France by the treaty of Aix-la-Chapelle, and Vauban fortified it. During the French occupation the town was considerably extended, and its fortifications strengthened to resist the attacks of William of Orange. In 1794 Charleroi again fell into the hands of the French, and it was dismantled by them. In 1816 it was re-fortified under Wellington's direction, but was finally dismantled in Parts of the old ramparts are left near the railway station. The battle of Charleroi (Aug. 22-23, 1914) was fought on the banks of the Sambre between the V. German Army and the retreating French troops.