Operation Overlord was the code name for the Battle of Normandy, the Allied operation that launched the successful invasion of German-occupied western Europe during World War II. The operation commenced on 6 June 1944 with the Normandy landings (Operation Neptune, commonly known as D-Day). A 1,200-plane airborne assault preceded an amphibious assault involving more than 5,000 vessels. Nearly 160,000 troops crossed the English Channel on 6 June, and more than two million Allied troops were in France by the end of August.

The Invasion of Normandy was the invasion by and establishment of Western Allied forces in Normandy, during Operation Overlord in 1944 during World War II; the largest amphibious invasion to ever take place.