France formed a formal alliance with the United States in 1778 during the American Revolutionary War.
The Treaty of Alliance was signed in Paris on February 6, 1778, alongside a Treaty of Amity and Commerce. France recognized the United States as an independent nation and agreed to support it against Great Britain. The alliance followed the American victory at Saratoga in 1777, which demonstrated that the rebellion might succeed.
French assistance included money, weapons, military advisers, soldiers, and naval forces. French participation became especially important in the southern campaign and at Yorktown in 1781, where the French fleet helped prevent British reinforcement or escape by sea.
Spain and the Dutch Republic also opposed Britain during the wider conflict, but neither formed the same formal alliance with the United States in 1778. France's alliance was the first official military partnership between the new republic and a major European power.