Actually, if आप mean "short movie" then it IS a trick question!
Many believe that स्टीमर, स्टीमबोट Willie was their first fully animated short film. However, it was actually a silent movie called Plane Crazy. स्टीमर, स्टीमबोट Willie was the first one to be दिया a full soundtrack, which is what made it famous. Plane Crazy was the first the company ever made.
After स्टीमर, स्टीमबोट Willie's success however, Plane Crazy was re-released also with a full soundtrack.
But if आप mean feature length movie then it's Snow White. Not only was it Disney's first feature length movie, but it was also the world's first fully animated feature length movie.
The company sure was good at reaching milestones in एनीमेशन history!
P.S: Oswald the Lucky Rabbit was a cartoon animated द्वारा Walt डिज़्नी himself, but it did not come from डिज़्नी Studios. He and his boss had a disagreement about his salary, डिज़्नी left the studio and soon after opened up his own.