An antagonist (from Greek ανταγωνιστής - antagonistes, "opponent, competitor, rival"^[1][2]) is a character, group of characters, or an institution, who represents the opposition against which the protagonist(s) must stop. In other words, 'A person, or a group of people who oppose the main character, or the main characters.'^[3] In the classic style of story where in the action consists of a hero fighting a villain, the two can be regarded as protagonist and antagonist, respectively.^[4] Contrary to popular belief, the antagonist is not always the villain, but simply those who oppose the main character.

The protagonist is in no way, always the "good guy". Writers have also created more complex situations. In some instances, a story is told from the villain's point of view, and any hero trying to stop the villain can be regarded as an antagonist. In the film K-19: The Widowmaker, an American film about a Soviet Cold War submarine crew, the crew, enemies of the United States, are depicted as protagonists, creating something of a paradox — as very often the American film industry tends to depict the forces of the United States as the people that fight for "good" and "justice", in opposition to Russia (especially the former Soviet Union) being the antagonists, who often have maniacal and/or malicious intentions (e.g. world domination). Such antagonists are usually police officers, or other law enforcement officials. Sometimes, antagonists and protagonists may overlap, depending on what their ultimate objectives are considered to be.

Various examples from modern films and television shows.

• Agon
• Protagonist
• False protagonist