Factual error: All swords in this movie are made from steel, and in the beginning it's said that the film takes place years before the Pyramids were built (they were built around 3200 BC). Steel wouldn't be around for 2000 more years. (00:03:50 - 00:12:40)
Factual error: The scientist claims that he is working on a magic powder (gunpowder) that was devised by the Chinese. Firstly, the Egyptians had no knowledge of the Chinese in those times and secondly, the Chinese didn't invent the gunpowder for at least another 4,000 years. (00:27:00)
Factual error: During Memnon's training session, at least one of his opponents uses a Japanese training sword known as a shinai. You can see this most clearly after the fight, when one of the weapons lying on the ground comes into view. Not only did the Egyptians and Japanese not have any contact with each other at this time, but this particular training weapon had not yet been invented.
Factual error: In the very beginning of the movie, when Mathayus rescues Jesup, he fires several arrows at Jesup's would-be executioners, and the targets of these arrows fly backward, across the room, and smash out the side of the building. I don't think I need to go into a detailed discussion of physics on this. (00:02:00)
Factual error: In this movie, camels seem to be a common sight in Egypt. However, these animals did not appear in the Nile valley until ca 8-900 BC - more than 2,000 years after this movie takes place. (00:08:10)