A villain (also known as the "antagonist," "baddie", "bad guy", "heavy" or "black hat") is an "evil" character in a story, whether a historical narrative or, especially, a work of fiction.

The villain usually is the antagonist (though can be the protagonist), the character who tends to have a negative effect on other characters. A female villain is occasionally called a villainess (often to differentiate her from a male villain). Random House Unabridged Dictionary defines villain as "a cruelly malicious person who is involved in or devoted to wickedness or crime; scoundrel; or a character in a play, novel, or the like, who constitutes an important evil agency in the plot".