The Kingdom of Belgium is divided into three regions. Two of these regions, Flanders and Wallonia, are each subdivided into five provinces. The third region, Brussels, does not belong to any province, nor is it subdivided into provinces. Instead, it has amalgamated both regional and provincial functions into a single "Capital Region" administration.

Most of the provinces take their name from earlier duchies and counties of similar location, while their territory is mostly based on the departments installed during French annexation. At the time of the creation of Belgium in 1830, only nine provinces existed, including the province of Brabant, which held the City of Brussels. In 1995, Brabant was split into three areas: Flemish Brabant, which became a part of the region of Flanders; Walloon Brabant, which became part of the region of Wallonia; and the Brussels-Capital Region, which became a third region. These divisions reflected political tensions between the French-speaking Walloons and the Dutch-speaking Flemish; the Brussels-Capital Region is officially bilingual.

The division into provinces is fixed by Article 5 of the Belgian Constitution. The provinces and Brussels are subdivided into 43 administrative arrondissements, and further into 565 municipalities.

The medieval Low Countries, including present-day Belgium, the Netherlands and Luxembourg, as well as parts of modern Germany and France, comprised a number of rival and independent feudal states of varying sizes. These each had their own identities and governments, though in the early modern period almost all the Belgian states became part of larger entities (the Seventeen Provinces (1549–1581) and the Southern Netherlands (after 1581)). Prominent early states in the area of modern Belgium included the Duchy of Brabant, the County of Flanders, the Prince-Bishopric of Liège and the Duchy of Luxembourg; smaller ones included the County of Hainaut, the Duchy of Limburg and the County of Namur, though there were other small states as well.

When these territories were annexed by France in 1795, they were reorganised into départments; the borders were redrawn and the historical names were replaced by names of geographical features (generally the main river of the area).

At the end of French rule and the creation of the United Kingdom of the Netherlands in 1815, the departmental territories were generally retained but were renamed into provinces and the historical names returned. At the time of the independence of Belgium from the Netherlands in 1830, Belgium's territory simply consisted of the existing nine southern provinces. The first article of the Belgian Constitution said: "Belgium is divided into provinces. These provinces are Antwerp, Brabant, West Flanders, East Flanders, Hainaut, Liège, Limburg, Luxembourg, Namur, except for the relations of Luxembourg with the German Confederation." As such, each of the modern provinces of Belgium (with the exception of Antwerp) takes its name from one of the medieval predecessors, whereas the borders largely correspond to those of the French departments, which in most cases differ substantially from the historical entities.

In 1839, as part of the Treaty of London, half of the province of Limburg became part of the Netherlands, which consequently has its own province of Limburg.

In 1920, following the First World War, Belgium annexed the Eupen-Malmedy territory, which became part of Liège Province.