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.

Hauts-de-Seine is a department in the Île-de-France region of France. It covers Paris's western inner suburbs. It is bordered by Paris, Seine-Saint-Denis and Val-de-Marne to the east, Val-d'Oise to the north, Yvelines to the west and Essonne to the south. With a population of 1,624,357 and a total area of 176 square kilometres, it has the second highest population density among all departments of France, after Paris. It is the fifth most populous department in France. Its prefecture is Nanterre, but Boulogne-Billancourt, one of its two subprefectures, alongside Antony, has a larger population.