Tiberius (Latin: Tiberius Julius Caesar Augustus; 16 November 42 BC – 16 March 37 AD), was Roman Emperor from 14 AD to 37 AD. Tiberius was by birth a Claudian, son of Tiberius Claudius Nero and Livia Drusilla. His mother divorced Nero and married Augustus in 39 BC, making him a step-son of Octavian. Tiberius would later marry Augustus' daughter Julia the Elder (from his marriage to Scribonia) and even later be adopted by Augustus, by which act he officially became a Julian, bearing the name Tiberius Julius Caesar. The subsequent emperors after Tiberius would continue this blended dynasty of both families for the next forty years; historians have named it the Julio-Claudian dynasty. In relations to the other emperors of this dynasty, Tiberius was the stepson of Augustus, great-uncle of Caligula, paternal uncle of Claudius, and great-great uncle of Nero.

Tiberius was one of Rome's greatest generals, conquering Pannonia, Dalmatia, Raetia, and temporarily Germania; laying the foundations for the northern frontier. But he came to be remembered as a dark, reclusive, and sombre ruler who never really desired to be emperor; Pliny the Elder called him tristissimus hominum, "the gloomiest of men." After the death of Tiberius’ son Drusus Julius Caesar in 23 he became more reclusive and aloof. In 26, against better judgement, Tiberius exiled himself from Rome and left administration largely in the hands of his unscrupulous Praetorian Prefects Lucius Aelius Sejanus and Quintus Naevius Sutorius Macro. Caligula, Tiberius' grand-nephew and adopted grandson, succeeded the emperor upon his death.