Caligula was a Roman emperor who lived from AD 12 to 41 and ruled for only a few years. Later Roman writers remember him as wildly cruel, violent, and not in his right mind — stories of killings, wild spending, and strange orders stuck to his name. How much of that is fair history, and how much is enemies talking after he was dead, is something scholars still argue about; the popular picture, though, is of a young emperor who went mad with power. He was murdered in AD 41. In English his name is now a shorthand for a ruler who is both cruel and out of control. It is a proper name, always written with a capital C.