The Battle of Grengam (Russian: Гренгамское морское сражение, Swedish: Slaget vid Ledsund, or Slaget vid Föglöfjärden.), Finnish: Flisön taistelu of 1720 was the last major naval battle in the Great Northern War that took place in Åland, in the Ledsund strait between the island communities of Föglö and Lemland. The battle marked the end of Russian and Swedish offensive naval operations in Baltic waters. The Russian fleet conducted one more raid on the Swedish coast in spring 1721, whereupon the Treaty of Nystad was signed, ending the war.