Actually, if 당신 mean "short movie" then it IS a trick question!
Many believe that 기선, 스팀 보트 Willie was their first fully animated short film. However, it was actually a silent movie called Plane Crazy. 기선, 스팀 보트 Willie was the first one to be given a full soundtrack, which is what made it famous. Plane Crazy was the first the company ever made.
After 기선, 스팀 보트 Willie's success however, Plane Crazy was re-released also with a full soundtrack.
But if 당신 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 애니메이션 history!
P.S: Oswald the Lucky Rabbit was a cartoon animated 의해 Walt 디즈니 himself, but it did not come from 디즈니 Studios. He and his boss had a disagreement about his salary, 디즈니 left the studio and soon after opened up his own.