300 is a comic book mini-series done by Frank Miller. It was later adapted into the film of the same name.
PlotKing Leonidas of Sparta gathered his 300 best men (hence the name) to stop a Persian invasion force despite being outnumbered. The deformed Ephialtes wanted to join, but due to his inability to lift his shield correctly (which would ruin their phalanx) was rejected. For two days and nights, the Spartans held off the Persians. After he failed to sway Leonidas to his side, the Persian king met with Ephialtes, who revealed to him a secret pass that would allow them to ambush the Spartans, which they do. So, the Spartans forced Dilios (a trusted aide) to leave, so he can tell their story. Despite being offered the chance to surrender (and have all his men alive), Leonidas goes on fighting, leading all the Spartans into getting killed. Later, Dilios told his troops about the story prior to the Battle of Plataea.
Both the movie and comic have criticized for egregious historical inaccuracy and the offensive way the so-called "Persians" were portrayed.