Union sportive Oyonnax Rugby is a French rugby union club from Oyonnax in the Ain département of the région Rhône-Alpes, currently competing in the first level of the French league system. They play their games at the Stade Charles-Mathon.
Founded in 1909 as Club Sportif Oyonnaxien and renamed Union Sportive Oyonaxienne in 1940. Oyonnax played in the regional leagues until 1967 when they joined the First Division. They were relegated to the lower divisions a few years later and bounced back to Group B of the First Division (the Second Division in fact) in 1988. Finally, in 2003 they reached the Fédérale 1 final and although they went down to Limoges (18-20), they moved on to the professional Pro D2. In the 2012/13 season, they won Pro D2 and were promoted to the top-flight Top 14.