Jemeppe-sur-Sambre is a municipality of Wallonia located in the province of Namur, Belgium. On 1 January 2006, the municipality had 17,990 inhabitants. The total area is 46.80 km2, giving a population density of 384 inhabitants per km². The municipality consists of the districts of: Balâtre, Ham-sur-Sambre, Jemeppe-sur-Sambre, Mornimont, Moustier-sur-Sambre, Onoz, Saint-Martin (including the hamlet of Villeret), and Spy. The Spy Cave, among the most significant Paleolithic sites in Europe, is located in the municipality. The medieval Balâtre Castle is in the village of Balâtre, and Mielmont Castle is in Onoz.