Royale Union Saint-Gilloise is a Belgian professional football club originally located in the municipality of Saint-Gilles, Brussels, although since the 1920s it has been based at the Stade Joseph Marien in the neighbouring municipality of Forest. The club is one of the most successful in the history of Belgian football. Union won eleven Belgian championships between 1904 and 1935, making it the most successful Belgian club before World War II. The team colours are blue and yellow and its matricule is the n°10.