Gay Panic Defense is a term used to describe a certain type of defense against certain crimes, when defending in a court of law. Specifically, when a person claims to have committed a violent crime, attack, assault or murder against a person of the same gender because they allege that the person made romantic or sexual propositions, it is called "gay panic." The defense is usually unsuccessful in winning acquittals, but it is often successful at reducing culpability and mitigating punishments.

The rationale behind the argument is that a person can become so offended or outraged by the sexual or romantic interest of a homosexual that he or she is driven temporarily insane and commits an act that would not otherwise be of his or her character (such as murder). The defense is often criticized as being illogical, offensive, and based in ignorance.

The defense is often used in the United States of America, especially in Southern states, where disapproval of homosexuality is very common. It is believed that this defense's effectiveness is boosted by widespread social fear and disapproval of homosexuality.

This defense was used in the famous case against the murderers of gay bashing victim Matthew Shepard. The two accused claimed that Shepard propositioned them, and they were enraged to the point of violently murdering him. The use of the defense was successful in securing a conviction of Aaron James McKinney for second-degree rather than first-degree murder, but its use enraged many residents of Laramie, Wyoming, where the crime took place.