Roazhon Celtic Kop (RCK) is the principal organised supporter group associated with Stade Rennais FC.
Founded in 1991, the group is officially recognised by the club and is based in the lower Groupe Rose Mordelles stand at Roazhon Park.
RCK remained clearly active in 2026. Stade Rennais officially listed the group among associations organising away travel to Paris and Angers, and the club also referred directly to the RCK supporter zone in disciplinary communications during the season.