Relations between Bulgaria and the United States were first formally established in 1903, have moved from missionary activity and American support for Bulgarian independence in the late 19th century to the growth of trade and commerce in the early 20th century, to reluctant hostility during World War I and open war and bombardment in World War II, to ideological confrontation during the Cold War, to partnership with the United States in the North Atlantic Treaty Organization (NATO) and growing political, military and economic ties in the beginning of the 21st century.

Bulgarian–American Joint Military Facilities were established by a Defence Cooperation Agreement signed by the United States and Bulgaria in April 2006. Under the agreement, U.S. forces will train at these bases, which remain under Bulgarian command and under the Bulgarian flag.