The answer to this is probably. Beethoven, who was Mozart's junior, was granted by his Elector, Maximilian Franz, a leave of absence to go to Vienna in order to meet Mozart in March of 1787. While there exist no first-hand accounts from either Mozart or Beethoven about the meeting, biographies within about 60 years of Mozart's death talk about the meeting. So, yes, they most likely met, but we have almost no reliable data about what went down.