The Action of 4 August 1800 was a highly unusual naval engagement that took place off the Brazilian coast during the French Revolutionary Wars. A French frigate force that had been raiding British commerce off West Africa approached and attempted to attack a large convoy of valuable East Indiamen, large and heavily armed merchant vessels sailing from Britain to British India and China. The East Indiamen were escorted by the small British ship of the line HMS Belliqueux, but otherwise had to rely on their individual armament of 30 cannon to protect them from attack. Due to their large size, the East Indiamen could be mistaken for ships of the line at a distance, and the French commander Commodore Jean-François Landolphe was un-nerved when the convoy formed a line of battle. Assuming his target to be a fleet of powerful warships he turned to escape and the British commander, Captain Rowley Bulteel immediately ordered a pursuit. To preserve the impression of warships he also ordered four of his most powerful East Indiamen to join the chase.

The larger British ship Belliqueux rapidly out ran Landolphe's flagship Concorde, leaving Landolphe with no option but to surrender without any serious resistance. The rest of the French squadron continued to flee separately during the night, each pursued by two East Indiamen. After an hour and a half of pursuit, with darkness falling, the East Indiaman Exeter came alongside the French Médée, giving the impression by use of lights that she was a large ship of the line. Believing himself outgunned, Captain Jean-Daniel Coudin surrendered, only discovering his assailant's true identity when he came aboard. Horrified, he demanded to be allowed to return to his ship to continue the fight, but Captain Henry Meriton on Exeter refused. The action is the only occasion during the war in which a large French warship was captured by a British merchant vessel.