Boulogne-Billancourt is a wealthy and prestigious commune in the western suburbs of Paris, France, located 8.2 km from the centre of Paris. It is a subprefecture of the Hauts-de-Seine department and thus the seat of the larger arrondissement of Boulogne-Billancourt. It is also part of the Métropole du Grand Paris. Boulogne-Billancourt includes one island in the Seine: Île Seguin.