Braine-l'Alleud (Dutch: Eigenbrakel) is a Walloon municipality in the Belgian province of Walloon Brabant, about 20 kilometers south of Brussels. The Braine-l'Alleud municipality includes the former municipalities of Braine-l'Alleud proper, Ophain-Bois-Seigneur-Isaac, and Lillois-Witterzée. It also includes the hamlet of Sart-Moulin, the inverted name of which inspired Hergé’s Moulinsart castle. The famous Lion of Waterloo where the eponymous battle took place is in the territory of Braine-l'Alleud. Bordering Flanders, the town is home to a minority of Dutch-speakers.
Several archaeological finds point to prehistoric settlements in this area. The first historical mention of a parish on Braine-l'Alleud's current territory, then called Dudinsart, dates from 1131, date at which Godfrey I, Duke of Brabant ceded it to the Abbey of Gembloux. The Duke, however, still owned exempt land (or franchise) on this territory, as specified in a legal document by Henry I dated 1197. The name of the municipality changed to the current one, derived from “Braine”, former name of the stream that crosses its territory (now called the “Hain”), and “alleu”, a medieval French word designating exempt land. The latter name was added to the former to distinguish this community from two neighbouring ones also called Braine.