The Chaussée d'Alsemberg (French, pronounced [ʃo.se d‿al.sɛm.bɛʁɡ]) or Alsembergsesteenweg (Dutch, pronounced [ˈɑl.səm.bɛr(ə)x.səˌsteːn.ʋɛx]) is a major north–south road in Belgium, forming part of the N235. It runs from the Barrière de Saint-Gilles/Bareel van Sint-Gillis in the Brussels municipality of Saint-Gilles to the town of Braine-l'Alleud (Wallonia), covering almost 5.5 kilometres (3.4 mi) within the Brussels-Capital Region. Along its route, it passes through the municipalities of Forest, Uccle, Drogenbos, Linkebeek, Beersel and Alsemberg.
Until nos. 139 and 156, the road lies on the territory of Saint-Gilles. Within Forest, where only a short section of the road is located, it borders the Altitude Cent/Hoogte Honderd area to the west and Berkendael/Berkendaal to the east. After this, the street enters Uccle, crosses the N261 at Globe, then continues southwards until Calevoet/Kalevoet. Beyond the Brussels Region, it continues towards the south-east through Linkebeek and Beersel before reaching Alsemberg, where it changes its name to become the Eigenbrakelsesteenweg until the regional border. In Braine-l'Alleud, it becomes the Chaussée d'Alsemberg again.
The Chaussée d'Alsemberg has long been an important transport and commercial axis. Since the 19th century, it has been lined with residential buildings, shops and workshops, while public transport, including trams, has reinforced its role as a link between central Brussels and the southern periphery.