Cergy is a commune in the northwestern suburbs of Paris, France
. It is located 27.8 km (17.3 mi) from the center of Paris, in the "new town" of Cergy-Pontoise
, created in the 1960s, of which it is the central and most populated commune.Although neighboring Pontoise is the official préfecture (capital) of the Val-d'Oise département, the préfecture building and administration, as well as the department council (conseil général), are located inside the commune of Cergy, which is regarded as the de facto capital of Val-d'Oise. The sous-préfecture building and administration, on the other hand, are located inside the commune of Pontoise.