The German occupation of Belgium of World War I was a military occupation of Belgium by the forces of the German Empire between 1914 and 1918. Beginning in August 1914 with the invasion of neutral Belgium, the country was almost completely overrun by German troops before the winter of the same year as the Allied forces withdrew westwards. The Belgian government went into exile, while King Albert I and the Belgian Army continued to fight on a section of the Western Front. Under the German military, Belgium was divided into three separate administrative zones. The majority of the country fell within the General Government, a formal occupation administration ruled by a German general, while the others, closer to the front line, came under more repressive direct military rule.

The German invasion of Belgium was a military campaign which began on 4 August 1914. On 24 July, the Belgian government had announced that if war came it would uphold its neutrality. The Belgian government mobilised its armed forces on 31 July and a state of heightened alert was proclaimed in Germany. On 2 August, the German government sent an ultimatum to Belgium, demanding passage through the country and German forces invaded Luxembourg. Two days later, the Belgian government refused the German demands and the British government guaranteed military support to Belgium. The German government declared war on Belgium on 4 August; German troops crossed the border and began the Battle of Liège.