Caligula, real name Gaius Caesar (ad 12-41), Roman emperor (ad 37-41), born probably in Antium (now Anzio, Italy), the youngest son of the Roman general Germanicus Caesar and the grandnephew of the Roman emperor Tiberius. His early life in military camps earned him the nickname Caligula (Latin, “Little Boot”) because of his small military shoes. Tiberius named his grandson, Tiberius Gemellus, and Caligula joint heirs to the throne, but the Roman Senate and people unwisely opted for Caligula as sole emperor. Caligula adopted Gemellus as his son but later had him murdered. A clement ruler for the first six months, he became a vicious tyrant after a severe illness. Historians believe that he probably went insane. He squandered his fortune on public entertainment and building projects; banished or murdered most of his relatives; had people tortured and killed while he dined; made his favourite horse a consul; declared himself a god; and had temples erected and sacrifices offered to himself. In 41 the officers of his guard formed a conspiracy against him, and he was assassinated.