Factual error: Much like its predecessor, this movie sorta speedruns through emperors; Geta and Caracalla here are shown as both ruling Rome as "twin emperors" in 200 AD, and die within a couple of days of each other, betrayed by Macrinus, who dies the same day. None of that is anywhere close to how things happened, to the point that discussing dates is sorta pointless; nothing resembles history if not in the loosest sense. Macrinus in this movie is never even formally proclaimed emperor, as opposed to him ruling for at least a full year.
Factual error: The movie begins in 200 AD, and the victorious general Acacius celebrates triumph and reports to the twin emperors that he conquered Numidia in their name. This may be less of an accomplishment than it appears when you consider that Numidia had already been a Roman province for centuries.
Other mistake: Macrinus and one of his high-ranking friends are discussing Lucilla's son, who disappeared when Commodus died. The guy says that Lucius disappeared when he was "about 12," but in the original Gladiator, he was barely about to turn 8. They also say these events happened 16 years prior, but, again according to the movie lore (without even looking at history), he died in 180 AD, and this movie is set in 200 AD.
Continuity mistake: When Macrinus is poisoning Caracalla's mind, telling him about supposed plans of his brother to use him as a scapegoat, Caracalla shouts, "That's a LIE, he's... he always LIES." The cup suddenly switched hands.
