Abstract: Self-defense is undergoing an epochal transformation. In the last few years, dozens of states have passed or proposed new Castle Doctrine legislation intended to expand the right to use deadly force in self-defense. These bills derive their informal name from the traditional common law castle doctrine, which grants a person attacked in his own home the right to use deadly force without trying to retreat to safety. But the new Castle Doctrine statutes, conceived and advocated by the National Rifle Association, extend beyond the home to self-defense more broadly. This Article sets out to explicate, contextualize, and theorize this remarkable development in self-defense law. To do so, the Article investigates the ideas that shape these new Castle Doctrine laws. It offers an interpretive genealogy focused on three crucial turning points in the development of self-defense, and argues that each has left a defining ideological trace on the new laws. The central claim is that in each phase, self-defense law drew importantly but differently on the idea of the home; and, in each, the operative idea of the home was constituted specifically by gender roles therein. The Article shows that modern self-defense law exemplified by the new Castle Doctrine powerfully embeds these distinctive meanings of gender, home, and crime.