Gaius Julius Caesar Augustus Germanicus (31 August AD 12 – 24 January AD 41), also called Gaius and Caligula, was the third Roman emperor, ruling from AD 37 until his assassination in AD 41. He was the son of the Roman general Germanicus and Augustus' granddaughter Agrippina the Elder, members of the first ruling family of the Roman Empire. He was born two years before Tiberius became emperor. Gaius accompanied his father, mother and siblings on campaign in Germania, at little more than four or five years old. He had been named after Gaius Julius Caesar, but his father's soldiers affectionately nicknamed him "Caligula" ('little boot').
 
During his brief reign, Caligula worked to increase the unconstrained personal power of the emperor, as opposed to countervailing powers within the principate. He directed much of his attention to ambitious construction projects and public works to benefit Rome's ordinary citizens, including racetracks, theatres, amphitheatres, and improvements to roads and ports. He began the construction of two aqueducts in Rome: the Aqua Claudia and the Anio Novus. During his reign, the empire annexed the client kingdom of Mauretania as a province. He had to abandon an attempted invasion of Britain, and the installation of his statue in the Temple in Jerusalem. In early 41, Caligula was assassinated as a result of a conspiracy by officers of the Praetorian Guard, senators, and courtiers. At least some of the conspirators might have planned this as an opportunity to restore the Roman Republic and aristocratic privileges. If so, their plan was thwarted by the Praetorians, who seem to have spontaneously chosen Caligula's uncle Claudius as the next emperor. Caligula's death marked the official end of the Julii Caesares in the male line, though the Julio-Claudian dynasty continued to rule until the demise of Caligula's nephew, the Emperor Nero.