The Battle of Leyte Gulf was the largest naval battle of World War II and by some criteria the largest naval battle in history, with over 200,000 naval personnel involved. It was fought in waters near the Philippine islands of Leyte, Samar, and Luzon from 23 to 26 October 1944 between combined American, Australian and Filipino forces and the Imperial Japanese Navy (IJN), as part of the invasion of Leyte, which aimed to isolate Japan from the colonies that it had occupied in Southeast Asia, a vital source of industrial and oil supplies.

The "largest naval battle in history" is a disputed title between adherents of varying criteria which include the numbers of personnel and/or vessels involved in the naval battle, the total displacement of the vessels involved and sometimes the significance and/or implications of the battle. While battles fought in modern times are comparatively well-documented, the figures from those in pre-Renaissance era are generally believed by contemporary chroniclers to be exaggerated.