It's reported to be two hours and fifteen minutes long, almost 30 mins shorter than the Chamber of Secrets.
Producer Chris Columbus said: "Every kid who saw the movies wanted them to be longer and almost every adult wanted them shorter."
Columbus added: "But I think this movie is so good that I don't think you'll get a lot of gripes."
Instead Mexican director Alfonso Cuaron is making the decisions, and he's kept his film shorter.
All the trailers and pictures from POA look really cool, but news the film isn't as long as the first two may surprise some fans.
Filming on the fourth film, The Goblet of Fire, has already started, this time directed by Brit Mike Newell.
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