Jonas Slier (22 March 1886 in Amsterdam – 5 November 1942 in Auschwitz concentration camp) was a Dutch gymnast who competed in the 1908 Summer Olympics. Jonas Slier was part of the Dutch gymnastics team, which finished seventh in the team event. In the individual all-around competition he finished 96th. There is no evidence that another Jonas Slier, the uncle of Philip Slier was the athlete mentioned above.