Boulogne-Billancourt. Boulogne-Billancourt (French pronunciation: ???[bul???? bij????ku??]; often colloquially called simply Boulogne, until 1924 Boulogne-sur-Seine, [bul???? sy?? s??n]) is a wealthy and prestigious commune in the Parisian area, located 8 km (5 mi) from its centre. It is a subprefecture of the Hauts-de-Seine department and thus the seat of the larger arrondissement of Boulogne-Billancourt. Boulogne-Billancourt includes two large islands in the Seine: ??le Saint-Germain and ??le Seguin. With a population of 121,334 as of 2018, it is the most populous commune in Hauts-de-Seine and most populous suburb of Paris, as well as one of the most densely populated municipalities in Europe.
