The earliest named inhabitants of Belgium were the Belgae (after whom modern Belgium is named). The population covered a significant area of Gaulish or Celtic Europe, living in northern Gaul at the time of the Roman occupation. The arrival of Germanic tribes from the north and east, is cited by Julius Caesar of Rome. Linguists have proposed that there is evidence that the Belgae had previously spoken an Indo European language intermediate between Celtic and Germanic.
Belgium has been ruled by a number of different groups since antiquity starting in the 1st century BC, when the Roman Republic created the province of Gallia Belgica. In the 5th century, the Bermanic Franks ruled. A gradual shift of power during the 8th century led the kingdom of the Franks to evolve into the Carolingian Empire. The Treaty of Verdun in 843 divided the region into a set of more or less independent fiefdoms under either of the King of France or the Holy Roman Empire.
The Eighty Years' War (1568–1648) divided the area into the northern area into the Seven United Provinces of the Netherlands and the Southern Netherlands. The South was the staging of most of the Franco-Spanish War (1635)|Franco-Spanish]] and War of the Austrian Succession (Franco-Austrian) wars.
Following the French Revolutionary Wars: the Low Countries — including territories that were never nominally under Habsburg rule were annexed by the French, ending Austrian rule in the region. The 1830 Belgian Revolution led to the establishment of an independent and neutral Belgium under a Provisional Government of Belgium and the establishment of the National Congress of Belgium. Since the installation of Leopold I of Belgium as king in 1831, Belgium has been a constitutional monarchy and parliamentary democracy.

The Berlin Conference of 1885 gave the Congo Free State to Leopold II as his private possession. From around 1900 there was growing international concern at the savage treatment of the Congolese population under Leopold II, for whom the Congo was primarily a source of revenue from ivory and rubber. In 1908 this outcry led the Belgian state to assume responsibility for the government of the colony.
Germany invaded Belgium in 1914 and much of the Western Front (World War). Belgium took over the German colonies of Rwanda and Burundi during the war, and they were mandated to Belgium in 1924 by the League of Nations. The country was again invaded by Germany in 1940 during the Blitzkrieg offensive, and occupied until its Allied advance from Paris to the Rhine in 1945. The Belgian Congo gained independence in 1960 during the Congo Crisis; Ruanda-Urundi followed two years later. After World War II, Belgium joined NATO as a founding member. Belgium now hosts major administrations and institutions for both NATO and the European Union..

City of Liege, Belgium
After World War II, Ghent and Antwerp experienced a rapid expansion of the chemical and petroleum industries. The 1973 and 1979 oil crises sent the economy into a recession. In the 1980s and 90s, the economic centre of the country continued to shift northwards and is now concentrated in the populous Flemish Diamond area. In 2005 and 2006, real GDP growth rates of 1.5% and 3.0%, respectively, were slightly above the average for the Euro area. From 1832 until 2002, Belgium's currency was the Belgian franc. Belgium switched to the euro in 2002, with the first sets of euro coins being minted in 1999.
Almost all of the Belgian population is urban—97% in 2004. The population density of Belgium is 342 per square kilometre—one of the highest in Europe, after that of the Netherlands and some microstates such as Monaco. The most densely inhabited area is the Flemish Diamond, outlined by the Antwerp–Leuven–Brussels–Ghent agglomerations. As of 2006, the Flemish Region had a population of about 6,078,600, with Antwerp (457,749), Ghent (230,951) and Bruges (117,251) its most populous cities; Wallonia had 3,413,978, with Charleroi (201,373), Liège (185,574) and Namur (107.178) its most populous. Brussels houses 1,018,804 in the Capital Region's 19 municipalities, two of which have over 100,000 residents.