According to the film's production blog:
Based on the epic graphic novel by Frank Miller, 300 is a ferocious retelling of the ancient Battle of Thermopylae in which King Leonidas (Gerard Butler) and 300 Spartans fought to the death against Xerxes and his massive Persian army.Sounds pretty cool. The last good sword-and-sandal epic was Gladiator. Since then we've had to endure Colin Farrell and his Pony-Boy haircut in Alexander and Brad Pitt with berettes in Troy. (both movies tied for the #1 spot on Ebert's 'Worst of 2004' list, but Alexander is far, far worse).