Grande-Synthe (; ) is a commune in the Nord department in the Nord-Pas de Calais region in northern France.
It is the second-largest suburb of the city of Dunkerque (Dunkirk) and lies adjacent to it on the west.
In 1980, a large part of Petite-Synthe was detached from Dunkerque and included in Grande-Synthe.
Grande-Synthe is twinned with: