The Action of 21 May 1565 was a naval battle in the Northern Seven Years' War, when the Swedes defeated the Danes. On 21 May, eight Danish ship were found north of Pomerania. They were there to prevent Swedish ships getting to or from Greifswald. Four of the ships fled into Greifswald to escape the Swedes but they chose to burn the other four ships to prevent them falling into enemy hands.