The club of CS Boussu-Bois was founded in 1918 in Boussu. In 1982, the club merged with CS Elouges, a club from the neighbouring town of Elouges, in the municipality of Dour, and was renamed Royal Francs Borains Boussu-Bois Elouges. In 1984–85, they won the Promotion B, 4th level of football in Belgium, and were promoted to the third division. At that moment, they simplified their name to Royal Francs Borains. The club became a third division regular, though they could not avoid relegation in 1994–95. After four seasons in the Promotion, Royal Francs Borains were back to the third level, and in 2008–09, they reached for the first time in their history the second level of football, under their new naming of Royal Boussu Dour Borinage. In 2009–10, they had their best ranking in their history, with a 5th place in the second division. Their highest league ranking was a 5th place in the second division in 2009–10.
In 2014, Boussu Dour Borinage sold their official matricule (167) to the owners of Seraing RUL (23) and bought itself the matricule 5192 of Royal Charleroi Fleurus, playing in the Belgian Fourth Division. As a result the team with matricule 167 moved to Seraing and was renamed Seraing United. It moved from the Stade Robert Urbain in Boussu to the Stade Pairay in Seraing. The Boussu Dour based team moved to the fourth division and was renamed Francs Borains. However, the results and history of the Boussu Dour based team remain with the matricule 167 and will be continued as Seraing United.