The Star Trek actor will portray the popular comic book character in Pete Travis's upcoming movie adaptation.
Urban made the announcement during an appearance on the New Zealand movie show Reel Late With Kate. "Yes, it's true, I am the law," he said, later adding that he is "thrilled to bits" with the role.
Written by 28 Days Later scribe Alex Garland, the film is said to be a closer adaptation of the original comics than Sylvester Stallone's 1995 outing.
Judge Dredd is scheduled to begin filming in the autumn.