Continuity mistake: During the scene in which Maximus battles one-on-one with Tigris of Gaul (the gladiator that returned from retirement) in the Coliseum, Maximus is ordered to kill the Tigris. As he refuses and throws the axe down, the left side of Maximus' neck is completely covered with blood. When Commodus enters to speak with Maximus, there is only the slightest trace of blood on his neck, which now also seems to be completely dry. (01:43:35 - 01:44:30)
Revealing mistake: When the chariot crashes in to the gladiators, we can see the shield in which the chariot crashes in to. It's not shaped like the other shields which are shaped in a perfect bow. This shield is rectangular shaped most likely to balance better on what ever is supporting it when the chariot runs over it making the chariot tip over. (01:30:00)
Audio problem: When Maximus is eating with Juba and Hagen, just before he fights Tigris of Gaul, listen to the background noise very closely as the men talk. There's lots of chatter and stray noises, but amid the sounds you can hear someone yelling urgently: "Warren, Warren... Warren...radio." This may be the sounds of a crew member telling another regarding a radio. (01:36:30)
Continuity mistake: In the battle scene between Maximus and Tigris, not only does the visor flip up and down (see above), but when Tigris falls down with his visor up, you can see that his face isn't marked. But when Maximus again unmasks Tigris, it's bloody with a giant scrape across the face. (01:42:35)
Factual error: The snake with red-yellow-brown skin you see in a night-shot in Rome is a Pueblan Milk Snake (Lampropeltis triangulum campbelli) from Mexico, also found in southern Texas. Not quite right for Rome... (02:04:15)
Factual error: There are several points in the film that show horses with saddles and stirrups. Pretty odd as the stirrup didn't arrive in Europe from China until the 3rd or 4th Century at the earliest.
Continuity mistake: During the battle of Carthage, Maximus rides past another man standing on the ground and throws a spear into his chest. The man clutches the spear with his right hand as he falls backwards, but when it cuts to him hitting the ground both his hands are out to the side and the spear has suddenly disappeared. (01:21:50)
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.