Boulogne-Billancourt is a wealthy and prestigious commune in the western suburbs of Paris, France, located 8.2 km (5 mi) 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.

Neuilly-sur-Seine, also known simply as Neuilly, is an urban commune in the Hauts-de-Seine department just west of Paris in France. Immediately adjacent to the city, north of the Bois de Boulogne, the area is composed of mostly select residential neighbourhoods, as well as many corporate headquarters and a handful of foreign embassies. One of the most affluent areas of France, it is the wealthiest and most expensive suburb of Paris.