France formally allied with the United States through the 1778 Treaty of Alliance during the American Revolution.
Signed in Paris on February 6, 1778, the treaty joined the American struggle with France's global conflict against Great Britain. Benjamin Franklin, Silas Deane, and Arthur Lee negotiated for the United States, while France was represented by Conrad Alexandre Gérard de Rayneval.
The agreement promised mutual support and stated that neither party would make a separate peace with Britain. France had already been providing covert assistance, including weapons, ammunition, and supplies. The alliance transformed that aid into an official military partnership.
French naval and land forces later played a decisive role in the Yorktown campaign. The treaty also had a diplomatic consequence: American negotiators had to balance their relationship with France while pursuing a separate peace with Britain. The alliance ended after the Treaty of Paris in 1783.