Cornwallis's Retreat was a naval engagement during the French Revolutionary Wars in which a British Royal Navy squadron of five ships of the line and two frigates was attacked by a much larger French Navy fleet of 12 ships of the line and 11 frigates. The action took place in the waters off the west coast of Brittany on 16–17 June 1795 (28–29 Prairial an III of the French Republican Calendar).

A British naval squadron under Vice-Admiral William Cornwallis began operating off Brittany on 7 June; in the following week he attacked a French merchant convoy and captured several ships. In response, Vice-admiral Villaret de Joyeuse led the main French fleet out of port to attack the British, who were spotted on 16 June. Heavily outnumbered, Cornwallis turned away from the French and attempted to escape into open water, with the French fleet in pursuit. After a full day's chase the British squadron lost speed, due to poorly loaded holds on two of their ships, and the French vanguard pulled within range on the morning of 17 June. Unwilling to abandon his rearguard, Cornwallis counter-attacked with the rest of his squadron. A fierce combat developed, culminating in Cornwallis interposing his flagship HMS Royal Sovereign between the British and French forces.

Cornwallis's determined resistance, and his squadron's signals to a group of unknown ships spotted in the distance, led Villaret de Joyeuse to believe that the main British Channel Fleet was approaching. Villaret therefore broke off the battle on the evening of 17 June and ordered his ships to withdraw. This allowed Cornwallis to escape; he returned to port at Plymouth with his squadron battered but intact. Villaret withdrew to an anchorage off Belle Île, close to the naval base at Brest. The French fleet was discovered there by the main British Channel Fleet on 22 June and defeated at the ensuing Battle of Groix, losing three ships of the line. Villaret was criticised by contemporaries for failing to press the attack on Cornwallis's force, whilst the British admiral was praised and rewarded for his defiance in the face of overwhelming French numerical superiority. The battle has since been considered by British historians to be one of the most influential examples "of united courage and coolness to be found in [British] naval history".