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

King Leonidas (Gerard Butler) leads 300 Spartans into battle against Persian "God-King" Xerxes (Rodrigo Santoro) and his army of more than one million soldiers. As the battle rages, 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.

Dilios, a Spartan soldier, narrates the story of Leonidas, from boyhood to the throne of Sparta. Years later, Persian messengers arrive at the gates of Sparta demanding it submit to King Xerxes.

Leonidas and his guards kick the messengers down a well. Knowing this will prompt a Persian attack, Leonidas visits the Ephors—ancient, leprosy-ridden priests whose blessing he needs before the Spartan council will authorize going to war. He proposes they repel the numerically superior Persians by using the terrain of Thermopylae (the Hot Gates), and funnel the Persians into a narrow pass between the rocks and the sea. The Ephors consult the Oracle Pythia, who decrees that Sparta must not go to war during their religous festival. As Leonidas departs an agent of Xerxes appears, who bribes the Ephors with concubines and money.

Leonidas follows his plan anyway, setting out with only 300 soldiers, which he calls his personal guard to avoid needing the council's permission. Though he knows it is a certain suicide mission, he hopes the sacrifice will spur the council to unite against Persia. Along the way to Thermopylae, the Spartans are joined by Arcadians and other Greeks. At Thermopylae, they construct a wall to contain the approaching Persian advance. Meanwhile, Leonidas meets Ephialtes of Trachis, a hunchbacked Spartan whose parents fled Sparta to spare him certain infanticide. Wanting to redeem his father's name, he asks to join Leonidas and warns him of a secret path the Persians could use to outflank and surround them. Though Leonidas is sympathetic to the eager warrior, he nevertheless turns him down, as Ephialtes cannot properly hold a shield, which would compromise the Spartans' phalanx formation.

Before 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 parleys with Leonidas, offering him wealth and power in exchange for his loyalty and surrender. Leonidas declines and Xerxes sends his elite guard, the feared Immortals, to attack them. The Spartans successfully dispatch them, but Ephialtes defects to the Persians and informs them of the secret path. When they realize Ephialtes' treachery, the Arcadians retreat and Leonidas orders Dilios to return to Sparta to tell the Council of their sacrifice. Though Dilios had recently lost his left eye in combat, he is still fit for battle, but Leonidas decides to use Dilios' gift for storytelling to appeal to the Spartan council. Though reluctant to leave his brothers behind, Dilios leaves with the Arcadians.

In Sparta, Gorgo, Queen of Sparta reluctantly submits sexually to the influential Theron in exchange for his 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 in a fit of anger. The dagger pierces his purse, spilling Persian coins from his robe.

The Council agrees 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 instead. Furious, Xerxes orders his troops to attack. Leonidas rises and hurls his spear at Xerxes, cutting the King on the cheek, thus making good on an earlier promise to make "the God-King bleed." Visibly disturbed by this reminder of his own mortality, Xerxes watches as all the Spartans are slaughtered by a massive barrage of arrows. Moments before his death, Leonidas pledges his undying love to Gorgo, his queen and wife.

Concluding his tale before an audience of Spartans on the edge of the battlefield a year after Thermopylae, Dilios relates how the Persian army is depleted by desertions, out of fear, and the heavy casualties they suffered at the hands of a mere 300 Spartans. Word of the valiant resistance of the 300 Spartans spread across Greece, inspiring the different city-states to unite against the Persians. Now the Persians face 10,000 Spartans commanding 30,000 Greeks. Although still outnumbered, Dilios declares that the Greeks shall be victorious, and praises the sacrifice of King Leonidas of Sparta. He then leads the Greeks in a charge against the Persian army, beginning the Battle of Plataea.