The Treaty of Neuilly-sur-Seine required Bulgaria to cede various territories, after Bulgaria had been one of the Central Powers defeated in World War I. The treaty was signed on 27 November 1919 at Neuilly-sur-Seine, France.

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.