Vespasiānus Augustus (17 November 9 – 23 June 79) was Roman emperor from AD 69 to AD 79. Vespasian founded the Flavian dynasty that ruled the Empire for twenty-seven years. Vespasian was from an equestrian family that rose into the senatorial rank under the Julio–Claudian emperors. Although he fulfilled the standard successionof public offices and held the consulship in AD 51, Vespasian's renown came from his military success: he was legate of Legio II Augustaduring the Roman invasion of Britain in 43 and subjugated Judaea during the Jewish rebellion of 66.

While Vespasian besieged Jerusalem during the Jewish rebellion, emperor Nero committed suicide and plunged Rome into a year of civil war known as the Year of the Four Emperors. After Galba and Othoperished in quick succession, Vitellius became the third emperor in April 69. The Roman legions of Roman Egypt and Judaea reacted by declaring Vespasian, their commander, emperor on 1 July 69. In his bid for imperial power, Vespasian joined forces with Mucianus, the governor of Syria, and Primus, a general in Pannonia, leaving his son Titus to command the besieging forces at Jerusalem. Primus and Mucianus led the Flavian forces against Vitellius, while Vespasian took control of Egypt. On 20 December 69, Vitellius was defeated, and the following day Vespasian was declared Emperor by the Senate. Vespasian dated his tribunician years from 1 July, substituting the acts of Rome's senate and people as the legal basis for his appointment with the declaration of his legions, and transforming his legions into an electoral college.

Little information survives about the government during Vespasian's ten-year rule. He reformed the financial system at Rome after the campaign against Judaea ended successfully, and initiated several ambitious construction projects. He built the Flavian Amphitheatre, better known today as the Roman Colosseum. In reaction to the events of 68–69, Vespasian forced through an improvement in army discipline. Through his general Agricola, Vespasian increased imperial expansion in Britain. After his death in 79, he was succeeded by his eldest son Titus, thus becoming the first Roman Emperor to be directly succeeded by his own natural son and establishing the Flavian dynasty