The French naval commander who defeated the British fleet in Chesapeake Bay was the Comte de Grasse.
The Battle of the Chesapeake, also called the Battle of the Capes, took place on September 5, 1781. A French fleet commanded by François Joseph Paul de Grasse fought a British fleet led by Rear Admiral Thomas Graves. Although the battle was tactically inconclusive in terms of captured ships, the British fleet withdrew and did not break the French control of the bay.
That naval result was strategically decisive. French ships blocked the sea route to Yorktown, Virginia, where British Lieutenant General Charles Cornwallis was surrounded by American and French land forces. Without naval relief, Cornwallis’s army faced bombardment and eventual surrender on October 19, 1781.
De Grasse commanded the French fleet from his flagship Ville de Paris. His victory demonstrated how French naval power, American troops, and French soldiers combined in the campaign that effectively ended major fighting in North America.