Union Sportive de Boulogne-sur-Mer Côte d'Opale (French pronunciation: [juːnjən spɔrtɪv bulɔɲ syʁ mɛʁ koʊt dopal]; commonly referred to as US Boulogne or simply Boulogne) is a French association football club based in the commune of Boulogne-sur-Mer. The club was founded in 1898 and currently plays in Championnat National, the third division of French football, having been relegated from Ligue 2 during the 2011–12 season.

The club was formed in 1898 and its achievements are minor with their biggest feat consisting of reaching the semi-finals during the 1936–37 edition of the Coupe de France. Boulogne play their home matches at the Stade de la Libération, which seats 15,004 having previously seated only 7,000 prior to its renovation in 2007.

US Boulogne were founded in December 1898 by a group of young athletes. While they mainly focussed originally on athletic events, they moved into the football industry and made a decent job in their first few years as a football club. Boulogne won the Maritime Championship three years running between 1904 and 1906. They next won the Championship in 1909 and their final victory of this division was in 1922. In 1924, Boulogne moved to the Northern Championship and fared well. The team also did well in the Coupe de France – reaching the quarter-finals in 1929 and the last 16 three times.