Basada en la épica novela gráfica de Frank Miller, 300 narra una vez más de manera atroz la antigua Batalla de Termópilas, en la que el rey Leónidas (Gerard Butler), junto con 300 espartanos, luchó a muerte contra el Emperador Jerjes y su gran ejército persa. Haciendo frente a insuperables adversidades, el valor y sacrificio de estos hombres inspiró a toda Grecia para unirse contra el enemigo persa, y así decir basta a esa situación en favor de la democracia. La película hace cobrar vida a la aclamada novela gráfica de Miller (Sin City) al combinar la acción real con fondos digitales que reproducen su marcada visión de este antiguo cuento histórico.

In the Battle of Thermopylae of 480 BC an alliance of Greek city-states fought the invading Persian army in the mountain pass of Thermopylae. Vastly outnumbered, the Greeks held back the enemy in one of the most famous last stands of history. Persian King Xerxes lead a Army of well over 100,000 (Persian king Xerxes before war has about 170,000 army) men to Greece and was confronted by 300 Spartans, 700 Thespians and other Slave soldiers. Xerxes waited for 10 days for King Leonidas to surrender or withdraw left with no options he moved. The battle lasted for about 3 days and after which all 300 Spartans were killed. The Spartan defeat was not the one expected, as a local shepherd, named Ephialtes, defected to the Persians and informed Xerxes of a separate path through Thermopylae, which the Persians could use to outflank the Greeks.