Sir Ridley Scott disowned the theatrical cut. He claims that the Director's Cut is the definitive version.
Edward Norton was briefly considered for the role of Guy, but upon reading the script he lobbied for the role of King Baldwin. Because the King appears behind a mask, he requested not to be credited. However, his name was put back in the video releases of the film.
In real life, Balian of Ibelin was a legitimate nobleman born in the Kingdom of Jerusalem.
Three 60-foot siege towers were built for the film, using the technology of the period. Each one weighed 25 tons. To accomplish the scene where a number of siege towers collapse, one of the real towers was knocked over on set and filmed from 11 different positions and locations. Various shots of the single tower falling were then composited together to give the impression that several towers had collapsed in different ways and in different directions.
Director Sir Ridley Scott and writer William Monahan felt that the unnamed character played by David Thewlis was an embodiment of God, or at the very least, an angel on a mission from God. This is not at all apparent in the theatrical cut, but in the Director's Cut, there are two scenes which strongly hint at it--one where the character seemingly disappears after a conversation with Balian (Orlando Bloom), the other where he seems to "resurrect" Balian after he is attacked and injured by three assassins.