Otho in the context of "Parallel Lives"

The 1st century was the century spanning AD 1 (represented by the Roman numeral I) through AD 100 (C) according to the Julian calendar. It is often written as the 1st century AD or 1st century CE to distinguish it from the 1st century BC (or BCE) which preceded it. The 1st century is considered part of the Classical era, epoch, or historical period. The Roman Empire, Han China and the Parthian Persia were the most powerful and hegemonic states.

During this century, the Roman Empire (ruled by the Julio-Claudian and Flavian dynasties) continued to be in a period of relative stability known as Pax Romana, withstanding a financial crisis in 33 and a civil war in 69. In Europe, Rome expanded into Britain and fought wars in Germania and Dacia. In Africa, Rome was challenged by Tacfarinas, who led his own Musulamii tribe and a loose and changing coalition of other Berber tribes before being defeated in 24. In West Asia, Rome defeated a Jewish rebellion (66–73) and fought a war with Parthia from 58–63, though the latter conflict was inconclusive. In East Asia, the Chinese Western Han dynasty was overthrown and replaced by the Xin dynasty in 9, which in turn faced its own rebel movements (namely the Red Eyebrows and Lulin), and was replaced by the Eastern Han dynasty in 25. The Eastern Han dynasty then faced and quelled a rebellion by the Trưng sisters (40–43). In 58, the Eastern Han dynasty entered a golden age with the Rule of Ming and Zhang, who were generally regarded as able administrators who cared about the common welfare of the people and who promoted officials with integrity. On its northern frontier, the Chinese dynasties waged intermittent war with the Xiongnu before emerging victorious in 91. The states of Funan and Xianbei were also established in this century.

The Year of the Four Emperors, AD 69, was the first civil war of the Roman Empire, during which four emperors ruled in succession, Galba, Otho, Vitellius, and Vespasian. It is considered an important interval, marking the change from the Julio-Claudians, the first imperial dynasty, to the Flavian dynasty. There were several rebellions and claimants, with shifting allegiances and turmoil in Rome and the provinces.

In 68, Vindex, legate of Gallia Lugdunensis, revolted against Nero and encouraged Galba, governor of Hispania, to claim the Empire. The latter was proclaimed emperor by his legion in early April. He was notably supported by Otho, legate of Lusitania. Soon after, the legate of a legion in Africa, Clodius Macer, also rebelled against Nero. Vindex was defeated by the Rhine legions at the Battle of Vesontio, but they too rebelled against Nero. On 9 June 68, Nero took his own life after being declared a public enemy by the Senate, which made Galba the new emperor. Galba was unable to establish his authority over the Empire, as several of his supporters were disappointed by his lack of gratitude. He especially adopted Piso Licinianus as heir (Galba was childless and elderly), instead of Otho, who, it had widely been assumed, would be chosen. Angered by this disgrace, Otho murdered Galba on 15 January with the help of the Praetorian Guard, and became emperor instead. Unlike Galba, he rapidly earned considerable popularity, notably by bestowing favours and emulating Nero's successful early years.

The Flavian dynasty, lasting from 69 to 96 CE, was the second dynastic line of emperors to rule the Roman Empire following the Julio-Claudians, encompassing the reigns of Vespasian and his two sons, Titus and Domitian. The Flavians rose to power during the civil war of 69 CE, known as the Year of the Four Emperors; after Galba and Otho died in quick succession, Vitellius became emperor in mid 69. His claim to the throne was quickly challenged by legions stationed in the eastern provinces, who declared their commander Vespasian emperor in his place. The Second Battle of Bedriacum tilted the balance decisively in favor of the Flavian forces, who entered Rome on 20 December, and the following day, the Roman Senate officially declared Vespasian emperor, thus commencing the Flavian dynasty. Although the dynasty proved to be short-lived, several significant historic, economic and military events took place during their reign.

The reign of Titus was struck by multiple natural disasters, the most severe of which was the eruption of Mount Vesuvius in 79 CE, which saw the surrounding cities of Pompeii and Herculaneum be completely buried under ash and lava. One year later, Rome was struck by fire and a plague. On the military front, the Flavian dynasty witnessed the siege and destruction of Jerusalem by Titus in 70 CE, following the failed Jewish rebellion of 66. Substantial conquests were made in Great Britain under the command of Gnaeus Julius Agricola between 77 and 83 CE, while Domitian was unable to procure a decisive victory against King Decebalus in the war against the Dacians. In addition, the Empire strengthened its border defenses by expanding the fortifications along the Limes Germanicus.

De vita Caesarum (Latin; lit. "On the Life of the Caesars"), commonly known as The Twelve Caesars or The Lives of the Twelve Caesars, is a set of twelve biographies of Julius Caesar and the first 11 emperors of the Roman Empire during the Principate. The subjects are Julius Caesar, Augustus, Tiberius, Caligula, Claudius, Nero, Galba, Otho, Vitellius, Vespasian, Titus, Domitian.

The Twelve Caesars was written in 121 CE by Gaius Suetonius Tranquillus (called "Suetonius" by scholars) while he served as a personal secretary to the emperor Hadrian. Suetonius dedicated the work to his friend, Gaius Septicius Clarus, a praetorian prefect.

Poppaea Sabina (30 AD – 65 AD), also known as Ollia, was a Roman empress as the second wife of the emperor Nero. She had also been wife to the future emperor Otho. The historians of antiquity describe her as a beautiful woman who used intrigues to become empress.

The large Villa Poppaea at Oplontis near Pompeii bears her name because of the archaeological finds there. It has been largely excavated and can be visited today.