Calais is a port city in the Pas-de-Calais department, of which it is a subprefecture. Although Calais is by far the largest city in Pas-de-Calais, the department's prefecture is its third-largest city of Arras. The population of the city proper is 67,544; that of the urban area is 144,625 (2020). Calais overlooks the Strait of Dover, the narrowest point in the English Channel, which is only 34 km (21 mi) wide here, and is the closest French town to England. The White Cliffs of Dover can easily be seen on a clear day from Calais. Calais is a major port for ferries between France and England, and since 1994, the Channel Tunnel has linked nearby Coquelles to Folkestone by rail.

The Pas-de-Calais is a department in northern France named after the French designation of the Strait of Dover, which it borders. It has the most communes of all the departments of France, with 890, and is the 8th most populous. It had a population of 1,465,278 in 2019. The Calais Passage connects to the Port of Calais on the English Channel. The Pas-de-Calais borders the departments of Nord and Somme and is connected to the English county of Kent via the Channel Tunnel.