Brussels (French: Bruxelles, pronounced [bʁysɛl]; Dutch: Brussel, pronounced [ˈbrʏsəl] ), officially the Brussels Region or Brussels-Capital Region (French: Région de Bruxelles-Capitale, Dutch: About this sound Brussels Hoofdstedelijk Gewest ), is the de facto capital city of the European Union (EU) and the largest urban area in Belgium. It comprises 19 municipalities, including the City of Brussels proper, which is the constitutional capital of Belgium, the seat of the French Community of Belgium and of the Flemish Community.

Brussels has grown from a 10th-century fortress town founded by a descendant of Charlemagne into a metropolis of more than one million inhabitants. The metropolitan area has a population of over 1.8 million, making it the largest in Belgium.

Since the end of the Second World War, Brussels has been a main centre for international politics. Its hosting of principal EU institutions as well as the headquarters of the North Atlantic Treaty Organization (NATO) has made the city a polyglot home of numerous international organisations, politicians, diplomats and civil servants.

Although historically Dutch-speaking, Brussels became increasingly French-speaking over the 19th and 20th centuries. Today a majority of inhabitants are native French-speakers, and both languages have official status. Linguistic tensions remain, and the language laws of the municipalities surrounding Brussels are an issue of much controversy in Belgium.