Factual error: After Napoleon's coup of the consul, there is a scene featuring Josephine carrying a toy Pomeranian dog. While Pomeranians existed at this time, they were much bigger in size (upwards of 50 pounds). The more modern type of Pomeranian that she is carrying wouldn't start coming about for another century.
Other mistake: After the failed invasion of Russia, the narration says out of the "600,000" that went into Russian, only 40,000 returned. That means 560,000 died. However at the end of the movie, Napoleon's losses are listed, the last one being "Invasion of Russia" where the dead are listed as "460,000" which is 100,000 off. (01:51:18 - 02:28:16)
Factual error: At his wedding to Josephine, Napoleon signs the certificate with his right hand. In fact, Napoleon was left-handed. (00:31:09)
Factual error: Marie Antoinette was not executed at Le Palais des Tuileries, as shown in the film, but rather at Place de la Concorde (formerly Place de la Révolution). Also, Napoleon did not witness the execution; he was on garrison duty in southern France at the time.
Factual error: Napoleon is riding a horse ahead of his soldiers to lead them into conflict with the enemy at Toulon (in 1795), Waterloo (in 1815), and elsewhere. While Napoleon could ride a horse (it was the only realistic mode of travel at the time), he was not a particularly skilled or accomplished horseman. He did little horse riding when at the military academy and when required to participate in combat at any level, he did so on foot.
Factual error: It is highly unlikely that Napoleon's mother, Letizia, staged a sexual encounter between him and a young woman to prove that he could have children. There was no need for such an experiment, since Napoleon had already fathered several illegitimate children, indicating that it was Josephine who was infertile.
Factual error: Napoleon never met the Duke of Wellington face to face, as is depicted in the film.