Martinus ("Tinus") Bernardus Osendarp (May 21, 1916 – June 20, 2002) was a Dutch athlete, excelling in the sprint events.

Born in Delft, Osendarp won two bronze medals at the 1936 Summer Olympics in the 100 and 200 m sprint events. The games were held in Nazi Germany and Osendarp gained some fame as the fastest white sprinter behind the black Americans, one of whom was Jesse Owens, who won both events. A possible third medal was lost when Osendarp dropped the baton in the final of the 4 x 100 m relay while fighting for second place.

At the European Championships in 1938 Osendarp won the titles on the 100 m and 200 m, equalling the performance of his compatriot Chris Berger who had accomplished the same feat in 1934.

As a police officer, Osendarp became a member of the German Security Service when Germany occupied the Netherlands in World War II. He later joined the Dutch national socialist NSB party and the SS.

In 1948, Osendarp was convicted for acts he committed during the war, although he was released early in 1952. After his release he moved to Limburg to work in the mines. He died in 2002 in Heerlen.