The Francization of Brussels (French: Francisation de Bruxelles, Dutch: Verfransing van Brussel) refers to the transformation of Brussels, Belgium, from a majority Dutch-speaking city to one that is bilingual or even multilingual, with French as both the majority language and lingua franca. Initially, the dominant aspect of this transition was the shift from Dutch to French among local Flemings in Brussels. This shift occurred over one or more generations, mirroring the advance of French elsewhere as a prestige language; subsequently, the dominance of French in Brussels has been further consolidated through internal migration of Francophone Walloons into the national capital, as well as by the immigration of non-Belgians, who either already speak French or adopt it on arrival.
A simultaneous shift from Walloon and Picard to Belgian French has taken place in Wallonia. A historical shift to French among urban elites in Leuven and Ghent has been reversed as the use of Dutch regained prestige.
The transition began very slowly in the 18th century, but accelerated after the Belgian Revolution, with Brussels as the capital of newly independent Belgium. In spite of the Dutch-speaking majority, French was made the sole official language, and French was the language of the government, the courts, culture, the media and education. The Dutch language had a low social prestige in Belgium at the time, and knowledge of French was considered necessary for social advancement, and Dutch-speakers suffered discrimination. The massive shift from Dutch to French was underway by the late 19th century. At first there was a surge in the number of bilingual residents, mostly native Dutch-speakers who had learned how to speak French, at the expense of monolingual Dutch-speakers. As Dutch was often not passed down from one generation to another, the number of monolingual Francophones in Brussels grew considerably. Halfway through the 20th century, the number of monolingual French-speakers surpassed the number of bilingual French/Dutch-speakers.