Charleroi (UKˈʃɑːrlə.rwʌ, US-rɔɪ,_-rwɑː, ʃaʁləʁwa; Tchålerwè tʃɑːlɛʀwɛ) is a city and a municipality of Wallonia, located in the province of Hainaut, Belgium. The city is situated in the valley of the Sambre, in the south-west of Belgium, not far from border with France. By 1 January 2008, the total population of Charleroi was 201,593. The metropolitan area, including the outer commuter zone, covers an area of with a total population of 522,522 by 1 January 2008, ranking it as the 5th most populous in Belgium after Brussels, Antwerp, Liège, and Ghent. The inhabitants are called Carolorégiens or simply Carolos.
The Charleroi area was already settled in the prehistoric period, with traces of metallurgical and commercial activities along the Sambre. Several public buildings, temples and villas were built in the area in the Roman period. Burial places, with jewels and weapons, have been found. The first written mention of a place called Charnoy dates from a 9th-century offering in the Lobbes abbey, which lists various neighboring towns and related tithe duties. During the Middle Ages, Charnoy was one of the many small hamlets in the area, with no more than about 50 inhabitants, part of the County of Namur.
Spanish territorial losses in the 1659 Treaty of the Pyrenees left a gap between the key fortresses of Mons and Namur; to fill this, Francisco Castel Rodrigo, then Governor of the Spanish Netherlands, expropriated land around Charnoy to build a fortress near the Sambre. In September 1666, it was renamed Charle-roi, or King Charles, in honour of five-year-old Charles II of Spain; the chronogram FVNDATVR CAROLOREGIVM (MDCLVVVI) can be found in the register of the parish of Charnoy.
Construction had only just begun when the War of Devolution with France began in 1667, and the Spanish withdrew. France retained the town under the 1668 Treaty of Aix-la-Chapelle, and its fortifications were completed by Vauban. A bridge was built over the Sambre, connecting the Ville Haute and Ville Basse, with incentives offered to persuade people to settle there.