The Special Relationship is a term that is often used to describe the political, social, diplomatic, cultural, economic, legal, environmental, religious, military and historic relations between the United Kingdom and the United States or its political leaders. The term first came into popular usage after it was used in a 1946 speech by former British Prime Minister Winston Churchill. Both nations have been close allies during many conflicts in the 20th and the 21st centuries, including World War I, World War II, the Korean War, the Cold War, the Gulf War and the war on terror.

Relations between the United Kingdom and the United States have ranged from military opponents to close allies since 1776. The Thirteen Colonies seceded from the Kingdom of Great Britain and declared independence in 1776, fighting a successful revolutionary war. While Britain was fighting Napoleon, the two nations fought the stalemated War of 1812. Relations were generally positive thereafter, save for a short crisis in 1861 during the American Civil War. By the 1880s, the US economy had surpassed Britain; in the 1920s, New York City surpassed London as the world's leading financial center. The two nations fought Germany together during the two World Wars; since 1940, the two countries have been close military allies, enjoying the Special Relationship built as wartime allies and NATO partners.