François Claessens (2 October 1897, Berchem - 29 September 1971, Antwerpen) was a Belgian gymnast who competed in the 1920 Summer Olympics.
In 1920 he was a member of the Belgian gymnastic team which won the silver medal in the team, European system event.
Also after the games he was active in sports.
In 1922 he competed in the "athletic Concours International de l´UIOCEP" in Brno (tsechoslovakia).