The Communauté d'agglomération Saint Germain Boucles de Seine is the communauté d'agglomération, an intercommunal structure, in the western suburbs of Paris. It is located in the Yvelines and Val-d'Oise departments, in the Île-de-France region, northern France. It was created in January 2016. Its population was 341,337 in 2014. Its seat is in Le Pecq.
The communauté d'agglomération consists of the following 20 communes, of which one (Bezons) in the Val-d'Oise department:
Coordinates: 48°54′N 2°07′E / 48.90°N 2.11°E