Is Troy based on a true story?

I'm curious, is the movie Troy based on a true story? It seems to portray historical events surrounding the Trojan War and the fall of Troy, but I'm not sure if it's an accurate representation of actual historical events. Are there any elements of the movie that are based on historical fact, or is it purely fictional? And if it is based on a true story, how closely does it adhere to the original events?