(63 BC-AD 14, reigned 27 BC-AD 14) was the first Roman emperor. Born Gaius Octavius, he was the grandnephew and heir of Julius Caesar. After Caesar was assassinated, Octavian formed the Second Triumvirate with Marc Antony and Marcus Lepidus to defeat Caesar's assassins. With the help of Marcus Agrippa, he sidelined Lepidus and defeated Antony at the Battle of Actium to seize the empire. Ruling as princeps, or first citizen, Augustus created the Praetorian Guard and added Egypt to the empire, but halted expansion into Germania after a crushing defeat at the Battle of Teutoburg Forest

(42 BC-AD 37, reigned AD 14-AD 37) was Augustus's stepson. During his father's reign, Tiberius led the conquests of Pannonia and Raetia in central Europe and became the imperial heir with the support of his mother Livia. Unhappy as emperor, he mostly resided in his island villa on Capri and left Lucius Sejanus to manage the state. However, when Sejanus attempted to seize power in AD 31, Tiberius had him arrested and executed. Tiberius was emperor when Jesus of Nazareth was crucified in AD 33.

(AD 12-AD 41, reigned AD 37-AD 41) was the son of Germanicus, Tiberius's popular nephew, and earned the nickname "Caligula," or little boot, from his father's soldiers. Though initially moderate, Caligula became increasingly tyrannical, supposedly trying to build a palace on Lake Nemi and to make his horse, Incitatus, a consul. In AD 41, Cassius Chaerea led a conspiracy of senators and Praetorian guards that killed Caligula and his immediate family.

(10 BC-AD 54, reigned AD 41-54 BC) was Caligula's uncle. A noted scholar, he was the last person able to read ancient Etruscan. He oversaw the conquest of Britain and centralized power through a bureaucracy featuring talented freedmen like Tiberius Narcissus. In AD 49, Claudius married his niece Agrippina the Younger, who then poisoned both Claudius's son Britannicus and the Emperor himself.

(AD 37-AD 68, reigned 54 BC-AD 68) was the son of Agrippina the Younger. He provoked scandal by performing as an actor and musician. He ordered his mother's death in AD 58, and ordered the deaths of Seneca the Younger and several others after the Pisonian Conspiracy. He supposedly "fiddled" during the Great Fire of Rome and persecuted Christians after it. In AD 68, he was deposed by the Senate and committed suicide.

(AD 53-AD 117, reigned AD 98-AD 117) led Rome to its greatest territorial extent. After succeeding Nerva, he defeated Decebalus to conquer the rich Kingdom of Dacia (modern-day Romania). He employed Apollodorus of Damascus to build Trajan's Column and Trajan's Bridge across the Danube. Near the end of his reign, he invaded the Parthian Empire, sacking its capital of Ctesiphon and annexing Armenia and Mesopotamia.

(76-138, reigned 117-138) was Trajan's younger cousin who succeeded him as emperor. At the start of his reign, he withdrew from Trajan's conquests in the east. While traveling in Greece, he joined the Eleusinian Mysteries; while visiting Egypt, his beloved companion Antinous drowned in the Nile. He also commissioned Hadrian's Wall to mark the border of Roman Britain and crushed the Bar Kokhba revolt in Judea.

(121-180, reigned 161-180) was the last of Rome's "Five Good Emperors." With Lucius Verus, he inherited the throne from his uncle Antoninus Pius and secured a decisive victory over the Parthian Empire. He then spent much of his reign dealing with the Antonine Plague and fighting the Marcomannic Wars. During this time he wrote the Meditations, a journal and major text of Stoic philosophy.

(244-305, reigned 284-305) stabilized the empire after the Crisis of the Third Century. He took power by defeating Carinus at the Battle of the Margus before creating the Tetrarchy, a new system of imperial rule with two senior emperors and two junior emperors. He unsuccessfully attempted to curb inflation with his Edict on Maximum Prices and led the last and largest persecution of Christians. In 305, he became the first emperor to voluntarily step down, retiring to his palace in Split, Croatia

(272-335, reigned 306-335) was the son of Constantius Chlorus, one of the junior members of Diocletian's Tetrarchy. Proclaimed emperor by his father's men, he defeated Maxentius at the Battle of Milvian Bridge to seize Italy and then defeated his brother-in-law Licinius to win the east. He proposed the Edict of Milan giving tolerance to Christians and oversaw the Christian Council of Nicea. He also converted the city of Byzantium into Constantinople, the capital of the Eastern Roman Empire for the next 1,100 years.

(AD 9-AD 79, reigned AD 69-AD 79) emerged from the Year of the Four Emperors in AD 69 to found the Flavian Dynasty, and later commissioned the Colosseum.

(145-211, reigned 193-211) triumphed in the Year of the Five Emperors and founded the Severan dynasty. He was the first emperor to be born in Africa.

(215-275, reigned 270-275) reconquered the territory lost during the Crisis of the Third Century by defeating Zenobia of the Palmyrene Empire and retaking Gaul and Britain.

(347-405, reigned 379-405) was the last man to rule both the eastern and western halves of the empire.

(460-507, reigned 475-476) is traditionally regarded as the last Roman emperor. He was deposed in 476 by Odoacer, marking the end of the Western Roman Empire.