Continuity mistake: At the beginning of the film, when the Romans are about to fight the Germanians, a shot of some soldiers standing beside a war machine is shown. In the background, you can see that the fires for the archers are already lit. The next shot then show the same fires being lit and you can tell they are in the same place as the ones previously shown.
Continuity mistake: Before Lucilla gets to Commodus who asks her if she knows if Gracchus has a new lover suspecting her to be his new lover, she walks by two servants. The servant on the left is looking down with his head bowed. When it cuts he is suddenly standing up straight looking after Lucilla as she walks by. (Extended version only). (02:08:35)Mortug
Continuity mistake: When Commodus goes to see his father thinking his father would pass his powers onto him, if you look closely when he enters, there's a white sheet blowing rather vigorously in front of the camera. When it cuts to a shot of Commodus, the sheet now is hardly blowing at all. (00:30:35)The-Immortal
Continuity mistake: At one point during the first Germanian attack you see the Roman soldiers creating a line-up with shields, soon after followed by the Germanians running towards them off-hill (starting their attack). Clearly a few Germanian stopped fighting a little too early and you see them (left-side) turning and looking around. (00:09:15)
Continuity mistake: Just before the battle with against the Germanians begins, while the Germanians are taunting the Romans, there are many arrows in the trees and in the ground. Twice we see this. Problem is that the disciplined Romans had not fired a single arrow at that point and no skirmishers, which could have been authorized to shoot before the order to "loose" can be seen in the open area in front of the defensive position. (00:06:50)
Continuity mistake: During the final scenes, when Maximus had died and his body is lying on the sand, we can see both the slaves and the Praetorians forming a semicircle around Maximus. When Quintus asks for help to carry Maximus body, during the second it takes long to raise it up (shot change), the slaves have moved and the Praetorians are forming a perfect honor corridor through which Maximus's body is about to go by. (02:20:55)
Continuity mistake: When we get to the comedy play fight between Maximus and Commodus, we look at the front of the stage and we see the actor playing Maximus is standing in the middle of the stage and the one playing Commodus on the right side. When we get a view from back of the stage 'Maximus' is standing on the left side of the stage and 'Commodus' in the middle. They have suddenly switched sides. (01:49:55)Mortug