The military history of the United Kingdom covers the period from the creation of the united Kingdom of Great Britain in 1707, with the political union of England and Scotland, to the present day.

From the 18th century, with the expansion of the British Empire and the country's industrial strength, Britain's military force became one of the largest and most powerful in the world, particularly its navy, with advanced technology and bases across the world. It declined during the 20th century in the wake of two world wars, decolonisation and the rise of the United States and the USSR as the new superpowers. Britain has been involved in a great many armed conflicts since the union in 1707, the majority alongside allies, on all continents except for Antarctica.

Today it still remains a major power with frequent military interventions across the globe since the end of the Cold War in 1990.

The British Military / Armed Forces, encompass the Royal Navy, the British Army, and the Royal Air Force.