A government in exile (abbreviated as GiE) is a political group that claims to be a country or semi-sovereign state's legitimate government, but is unable to exercise legal power and instead resides in a foreign country. Governments in exile usually plan to one day return to their native country and regain formal power. A government in exile differs from a rump state in the sense that a rump state controls at least part of its former territory. For example, during World War I, nearly all of Belgium was occupied by Germany, but Belgium and its allies held on to a small slice in the country's west. A government in exile, in contrast, has lost all its territory. However, in practice the difference might be minor; in the above example, the Belgian government at Sainte-Adresse was located in French territory and acted as a government in exile for most practical purposes.

The governments in exile tend to occur during wartime occupation or in the aftermath of a civil war, revolution, or military coup. For example, during German expansion and advance in World War II, some European governments sought refuge in the United Kingdom, rather than face destruction at the hands of Nazi Germany. On the other hand, the Provisional Government of Free India proclaimed by Netaji Subhas Chandra Bose sought to use support from the invading Japanese to gain control of the country from what it viewed as British occupiers, and in the final year of WWII, after Nazi Germany was driven out of France, it maintained the remnants of the Nazi-sympathizing Vichy government as a French government in exile at the Sigmaringen enclave.

A government in exile may also form from widespread belief in the illegitimacy of a ruling government. Due to the outbreak of the Syrian Civil War in 2011, for instance, the National Coalition for Syrian Revolutionary and Opposition Forces was formed by groups whose members sought to end the rule of the ruling Ba'ath Party.

The governments in exile may have little or no recognition from other states. The effectiveness of a government in exile depends primarily on the amount of support it receives, either from foreign governments or from the population of its own country. Some exiled governments come to develop into a formidable force, posing a serious challenge to the incumbent regime of the country, while others are maintained chiefly as a symbolic gesture.

The phenomenon of a government in exile predates the formal utilization of the term. In periods of monarchical government, exiled monarchs or dynasties sometimes set up exile courts, as the House of Stuart did when driven from their throne by Oliver Cromwell and again at the Glorious Revolution (see James Francis Edward Stuart § Court in exile). The House of Bourbon would be another example because it continued to be recognized by other countries at the time as the legitimate government of France after it was overthrown by the populace during the French Revolution. This continued to last through the rule of Napoleon Bonaparte and the Napoleonic Wars from 1803–04 to 1815. With the spread of constitutional monarchy, monarchical governments which were exiled started to include a prime minister, such as the Dutch government during World War II headed by Pieter Sjoerds Gerbrandy.