300 is a 2007 film adaptation of the graphic novel of the same name by Frank Miller, and is a fictionalized retelling of the Battle of Thermopylae. The film was directed by Zack Snyder while Miller served as executive producer and consultant. The film was shot mostly with a super-imposition chroma key technique, to help replicate the imagery of the original comic book.

Spartan King Leonidas (Gerard Butler) and 300 Spartans fight to the last man against Persian "God-King" Xerxes (Rodrigo Santoro) and his army of more than one million soldiers. As the battle rages, Spartan Queen Gorgo (Lena Headey) attempts to rally support in Sparta for her husband. The story is framed by a voice-over narrative by the Spartan soldier Dilios (David Wenham). Through this narrative technique, various fantastical creatures are introduced, placing 300 within the genre of historical fantasy.

300 was released in both conventional and IMAX theaters in the United States on March 9, 2007, and on DVD, Blu-ray, and HD DVD on July 31, 2007. The film's opening was the 24th largest in box office history, although critics were divided over its look and style. Some acclaimed it as an original achievement, while others criticized it for favoring visuals over characterization and its controversial depiction of the ancient Persians.

Through Dilios' narration, the life of young Leonidas is depicted, chronicling his journey from a boy to a man per Spartan doctrine. Years later, after Leonidas is crowned King, Persian messengers arrive at the gates of Sparta demanding its submission to King Xerxes. Offended by their threats and behavior, King Leonidas and his guards kick the messengers into a well. Knowing that these actions will precipitate a Persian attack, Leonidas visits the Ephors -- ancient priests whose blessing he needs to convince the Spartan council to authorize going to war. He proposes a strategy to repel the numerically superior Persians by using the terrain of Thermopylae (the Hot Gates)—his plan involves funneling the Persians into a narrow pass between the rocks and the sea. The Ephors consult the Oracle, who decrees that Sparta must not go to war. After Leonidas departs a messenger from Xerxes appears, rewarding the Ephors for their covert support and revealing that they have been corrupted by Xerxes.

Denied by the Ephors, Leonidas follows his plan anyway. While he does not require the council's permission for this, taking such a small force, turns what had been a bold strategy into a certain suicide mission. Leonidas hopes that the sacrifice of himself and his men will spur the council to defy the Ephors and all of Greece to unite against the threat to freedom and democracy (represented by Greece) posed by slavery and tyranny (represented by Persia).

Along the way to Thermopylae, the Spartans are joined by Arcadians and various other Greeks. They construct a wall at Thermopylae to contain the approaching Persian advance. Meanwhile, Leonidas encounters Ephialtes, a hunchbacked Spartan whose parents fled Sparta to spare him certain infanticide. Ephialtes asks to redeem his father's name by joining Leonidas, warning him of a secret path the Persians could use to outflank and surround them. Leonidas is sympathetic to the eager warrior but rejects him, as Ephialtes cannot properly hold a shield, which would compromise the Spartans' phalanx formation.

Prior to the battle, the Persians demand that the Spartans lay down their weapons. Leonidas refuses, and with their tightly-knit phalanx formation the Spartans use the narrow terrain to repeatedly rebuff the advancing Persian army. Xerxes personally approaches Leonidas to persuade him to surrender, offering Leonidas wealth and power in exchange for his loyalty. Leonidas declines, promising instead to make the "God-King" bleed. Outraged, Xerxes sends in his elite guard, the Immortals, whom the Spartans dispatch. As the Spartans continue to defeat Xerxes' forces, Ephialtes defects to the Persian king and reveals the location of the secret path. When they realize Ephialtes' treachery, the Arcadians retreat. Leonidas orders a reluctant Dilios to return to Sparta to tell the Council of their sacrifice.

In Sparta, Queen Gorgo reluctantly submits sexually to the influential Theron in exchange for help in persuading the Spartan council to send reinforcements to Leonidas. Following her address to the Council, Theron publicly betrays the Queen, prompting the councilmen to cry out in outrage and Gorgo to kill him out of rage, which spills open a bag of Xerxes' gold from his robe. The exposure of Theron's treachery, along with their Queen's plea, prompts the Council to unite against Persia. Meanwhile, at Thermopylae, the Persians use the goat path to surround the Spartans. Xerxes' general demands their surrender, again offering Leonidas titles and prestige. Leonidas seemingly bows in submission, allowing one of his men to leap over him and kill the general. A furious Xerxes orders his troops to attack. As Persian archers shoot at the remaining Spartans, Leonidas rises and hurls his spear at Xerxes, cutting the Persian on the cheek, thus making good on his promise to make "the God-King bleed." Visibly disturbed by this reminder of his own mortality, Xerxes watches as all of the Spartans are cut down by a massive barrage of arrows. Concluding his tale before an audience of attentive Spartans, Dilios declares that the Persian army, depleted by desertions out of fear the heavy casualties they suffered at the hands of a mere 300 Spartans, now faces 10,000 Spartans commanding 30,000 Greeks. Although still outnumbered, Dilios declares that the Greeks shall have victory. Praising Leonidas' sacrifice, Dilios leads the assembled Greek army in a charge against the Persian army, igniting the Battle of Plataea.