Factual error: When the Trojans flee inside the walls at the arrival of the Greeks, you can see some llamas. Llamas were only known in Latin America and not in ancient Troy.
Factual error: More than once the sun is seen rising over the sea. But that would be impossible, since the sun rises in the east and the sea around Troy is in the north and west, not in the east.
Factual error: When King Priam is showing Paris the Sword of Troy we get a close-up view of the blade and it looks suspiciously like steel or polished iron, as do a lot of the weapons which we see in this film. However, at the time of the Trojan War, civilization was still very much rooted in the Bronze Age and iron weapons would not have been available. Iron weapons were first used by the Philistines around 1100 BC, some years after the Trojan War, and it was still another several hundred years before this technology was ever used.
Factual error: Probably the most common mistake in all the ancient warfare movies like Troy. The thick leather armour that soldiers wear is almost impossible to pierce with such crudely sharpened swords but they always seem to pierce the armour with effortless ease.
Factual error: When the Greek leaders are lining up to offer gifts to Agamemnon, one of them is carrying a red-figure vase shaped like a submarine. Red-figure pottery (made of red clay with a black glaze, from which lines and shapes are removed to make red images) was not made until the fifth century BC.
Factual error: The boy who is sent to retrieve Achilles, refers to Boagrius as the Thessalonian, speaking of those from Thessaly. Thessalonians are people from the Greek city of Thessalonika - which is settled about 1000 years AFTER the battle of Troy. People from Thessaly were/are called Thessalians. The term Thessalonian should never even have been known to the boy, much less used by him.