Chaumont-Gistoux is a Walloon municipality located in the Belgian province of Walloon Brabant. On 1 January 2006 Chaumont-Gistoux had a total population of 10,926. The total area is 48.09 km² which gives a population density of 227 inhabitants per km².
It was formed from the fusion, in 1977, of Dion-Valmont (itself a fusion in 1971 of Dion-le-Val and Dion-le-Mont), Bonlez, Corroy-le-Grand, Longueville and Chaumont-Gistoux. The administrative offices are now in the village of Gistoux.
It is a semi-rural commune with several working farms, large areas given over to fields and forests, although there is a major industry of sand extraction, now mostly in decline. Due to this history there are now several haulage and construction firms based in the commune.
Chaumont-Gistoux is on the KW-line, a defensive line erected early in the 2nd World War, intended to prevent invasion from Germany. A small museum houses information about the line and many exhibits from the war.
Her Royal Highness Princess Claire of Belgium grew up in Chaumont-Gistoux. The Coombs family still resides there to this day, and the Princess, her husband Prince Laurent and their children are often seen in the municipality.