The action of 18 August 1798 was a minor naval engagement of the French Revolutionary Wars, fought between the British fourth rate ship HMS Leander and the French ship of the line Généreux. Both ships had been engaged at the Battle of the Nile three weeks earlier, in which a British fleet under Rear-Admiral Sir Horatio Nelson had destroyed a French fleet at Aboukir Bay on the Mediterranean coast of Egypt. Généreux was one of only four French ships to survive the battle, while Leander had been detached from the British fleet by Nelson on 6 August. On board, Captain Edward Berry sailed as a passenger, charged with carrying despatches to the squadron under Earl St Vincent off Cadiz. On 18 August, while passing the western shore of Crete, Leander was intercepted and attacked by Généreux, which had separated from the rest of the French survivors the day before.

HMS Leander was a Portland-class 50-gun fourth rate of the Royal Navy, launched at Chatham on 1 July 1780. She served on the West Coast of Africa, West Indies, and the Halifax station. During the French Revolutionary Wars she participated in the Battle of the Nile before a French ship captured her. The Russians and Turks recaptured her and returned her to the Royal Navy in 1799. On 23 February 1805, while on the Halifax station, Leander captured the French frigate Ville de Milan and recaptured her prize, HMS Cleopatra. On 25 April 1805, cannon fire from Leander killed an American seaman while Leander was trying to search an American vessel off the US coast for contraband. The resulting "Leander affair" contributed to the worsening of relations between the United States and Great Britain. In 1813, the Admiralty converted Leander to a hospital ship under the name Hygeia. Hygeia was sold in 1817.