The Belgian Government in London, also known as the Pierlot IV Government, was the government in exile of Belgium between October 1940 and September 1944 during World War II. The government was tripartite, involving ministers from the Catholic, Liberal and Labour Parties. After the invasion of Belgium by Nazi Germany in May 1940, the Belgian government, under Prime Minister Hubert Pierlot, fled first to Bordeaux in France and then to London, where it established itself as the only legitimate representation of Belgium to the Allies.

Hubert Marie Eugène Pierlot was a Belgian politician and Prime Minister of Belgium, serving between 1939 and 1945. Pierlot, a lawyer and jurist, served in World War I before entering politics in the 1920s. A member of the Catholic Party, Pierlot became Prime Minister in 1939, shortly before Belgium entered World War II. In this capacity, he headed the Belgian government in exile, first from France and later Britain, while Belgium was under German occupation. During the German invasion of Belgium in May 1940, a violent disagreement broke out between Pierlot and King Leopold III over whether the King should follow the orders of his ministers and go into exile or surrender to the German Army. Pierlot considered Leopold's subsequent surrender a breach of the Constitution and encouraged the parliament to declare Leopold unfit to reign. The confrontation provoked a lasting animosity between Pierlot and other conservatives, who supported the King's position and considered the government's exile to be cowardly.