Nero Claudius Caesar Augustus Germanicus ( NEER-oh; born Lucius Domitius Ahenobarbus; 15 December AD 37 – 9 June AD 68), was the fifth Roman emperor and final emperor of the Julio-Claudian dynasty, reigning from AD 54 until his death in AD 68. He was adopted by the Roman emperor Claudius at the age of 13 and succeeded him on the throne. Nero was popular with the members of his Praetorian Guard and lower-class commoners in Rome and its provinces, but he was deeply resented by the Roman aristocracy. Most contemporary sources describe him as tyrannical, self-indulgent, and debauched. After being declared a public enemy by the Roman Senate, he committed suicide at age 30.

Nero was born at Antium in AD 37, the son of Gnaeus Domitius Ahenobarbus and Agrippina the Younger, a great-granddaughter of the emperor Augustus. When Nero was two years old, his father died. His mother married the emperor Claudius, who eventually adopted Nero as his heir; when Claudius died in AD 54, Nero became emperor with the support of the Praetorian Guard and the Senate. In the early years of his reign Nero was advised and guided by his mother Agrippina, his tutor Seneca the Younger, and his praetorian prefect Sextus Afranius Burrus, but he soon sought to rule independently and to rid himself of restraining influences. His power struggle with his mother was eventually resolved when he had her murdered. Roman sources also implicate Nero in the deaths of his wife Claudia Octavia – supposedly so that he could marry Poppaea Sabina – and of his step brother Britannicus.

Nero's practical contributions to Rome's governance focused on diplomacy, trade, and culture. He ordered the construction of amphitheaters, and promoted athletic games and contests. He also made public appearances as an actor, poet, musician, and charioteer, which scandalised his aristocratic contemporaries as these occupations were usually the domain of slaves, public entertainers and infamous persons. The provision of such entertainments made Nero popular among lower-class citizens, but his performances undermined the Imperial dignity. The costs involved were borne by local elites either directly or through taxation, and were much resented.

During Nero's reign, the general Corbulo fought the Roman–Parthian War of 58–63, and made peace with the hostile Parthian Empire. The Roman general Suetonius Paulinus quashed a major revolt in Britain led by the Iceni's queen Boudica. The Bosporan Kingdom was briefly annexed to the empire, and the First Jewish–Roman War began. When the Roman senator Vindex rebelled, with support from the eventual Roman emperor Galba, Nero was declared a public enemy and condemned to death in absentia. He fled Rome, and on 9 June AD 68 he committed suicide. His death sparked a brief period of civil war known as the Year of the Four Emperors.

Most Roman sources offer overwhelmingly negative assessments of his personality and reign. The historian Tacitus claims the Roman people thought him compulsive and corrupt. Suetonius tells that many Romans believed that the Great Fire of Rome was instigated by Nero to clear land for his planned "Golden House". Tacitus claims that Nero seized Christians as scapegoats for the fire and had them burned alive, seemingly motivated not by public justice but by personal cruelty. Some modern historians question the reliability of the ancient sources on Nero's tyrannical acts, considering his popularity among the Roman commoners. In the eastern provinces of the Empire, a popular legend arose that Nero had not died and would return. After his death, at least three leaders of short-lived, failed rebellions presented themselves as "Nero reborn" in order to gain popular support.