The Battle of Leyte Gulf (Filipino: Labanan sa Look ng Leyte) 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 and Australian forces and the Imperial Japanese Navy (IJN), as part of the invasion of Leyte, which aimed to isolate Japan from the countries it had occupied in Southeast Asia which were a vital source of industrial and oil supplies.

By the time of the battle, Japan had fewer capital ships (aircraft carriers and battleships) left than the Allied forces had total aircraft carriers, underscoring the disparity in force strength at this point in the war. Regardless, the IJN mobilized nearly all of its remaining major naval vessels in an attempt to defeat the Allied invasion, but it was repulsed by the U.S. Navy's Third and Seventh fleets.

The battle consisted of four main separate engagements: the Battle of the Sibuyan Sea, the Battle of Surigao Strait, the Battle off Cape Engaño and the Battle off Samar, as well as lesser actions.This was the first battle in which Japanese aircraft carried out organized kamikaze attacks, and the last naval battle between battleships in history. The Japanese Navy suffered heavy losses and never sailed in comparable force thereafter, stranded for lack of fuel in their bases for the rest of the war, and were therefore unable to affect the successful Allied invasion of Leyte.