France formally allied with the United States during the American Revolutionary War in 1778.
The Franco-American Alliance was signed on February 6, 1778, in Paris. France recognized the United States and agreed to provide military and financial support against Great Britain. The agreement followed France’s covert assistance to the American cause, including weapons and supplies.
French involvement became decisive after the alliance. French troops and naval forces participated in operations, and French support helped make possible the allied victory at Yorktown in 1781. The alliance also made the conflict an international war rather than a struggle limited to Britain and its former colonies.
France’s intervention damaged its finances, contributing to severe fiscal problems before the French Revolution. Spain also fought Britain during the wider conflict, but it did not sign the same formal alliance treaty with the United States in 1778.