The Rogožarski SIM-X (Serbian Cyrillic: Рогожарски СИМ-X) was a Yugoslav single-engine sports and tourist plane also used for basic training of military pilots designed in 1936, with two crew members.

The SIM-X was designed by Sima Milutinović at the beginning of 1936 drawing on positive experiences of its predecessors SIM-II and SIM-VIII.

The SIM-X was a single engine, high monoplane parasol wing, with a wooden double-shaft propeller, for two crew members seated in tandem.

[3] With the introduction of instrument flight training for military pilots in 1939, all Yugoslavian aircraft manufacturers tried to make a school plane for this purpose.

[6] There were five planes of this type in Aeroclub at the time, however just before the war broke out all SIM-X aircraft were redeployed.

The air forces of the Croatian Independent State used one SIM-X until 1943 when it was destroyed by the Srem partisans in emergency landing.