Octavian in the context of "Battle of Actium"

During the classical period, the Roman Empire controlled the Mediterranean and much of Europe, Western Asia, and North Africa. The Romans conquered most of these territories in the time of the Republic, and it was ruled by emperors following Octavian's assumption of power in 27 BC. Over the 4th century AD, the empire split into western and eastern halves. The western empire collapsed in 476 AD, while the eastern empire endured until the fall of Constantinople in 1453.

By 100 BC, the city of Rome had expanded its rule from the Italian peninsula to most of the Mediterranean and beyond. However, it was severely destabilised by civil wars and political conflicts, which culminated in the victory of Octavian over Mark Antony and Cleopatra at the Battle of Actium in 31 BC, and the subsequent conquest of the Ptolemaic Kingdom in Egypt. In 27 BC, the Roman Senate granted Octavian overarching military power (imperium) and the new title of Augustus, marking his accession as the first Roman emperor. The vast Roman territories were organized into senatorial provinces, governed by proconsuls who were appointed by lot annually, and imperial provinces, which belonged to the emperor but were governed by legates.

Marcus Antonius (14 January 83 BC – 1 August 30 BC), commonly known in English as Mark Antony, was a Roman politician and general who played a critical role in the transformation of the Roman Republic from a constitutional republic into the autocratic Roman Empire.

Antony was a relative and supporter of Julius Caesar, and he served as one of his generals during the conquest of Gaul and Caesar's civil war. Antony was appointed administrator of Italy while Caesar eliminated political opponents in Greece, North Africa, and Spain. After Caesar's assassination in 44 BC, Antony joined forces with Lepidus, another of Caesar's generals, and Octavian, Caesar's great-nephew and adopted son, forming a three-man dictatorship known to historians as the Second Triumvirate. The Triumvirs defeated Caesar's killers, the Liberatores, at the Battle of Philippi in 42 BC, and divided the government of the Republic among themselves. Antony was assigned Rome's eastern provinces, including the client kingdom of Egypt, then ruled by Cleopatra VII, and was given the command in Rome's war against Parthia.

The history of Rome includes the history of the city of Rome as well as the civilisation of ancient Rome. Roman history has been influential on the modern world, especially in the history of the Catholic Church, and Roman law has influenced many modern legal systems. Roman history can be divided into the following periods:

• Pre-historical and early Rome, covering Rome's earliest inhabitants and the legend of its founding by Romulus
• The period of Etruscan dominance and the regal period, in which, according to tradition, Romulus was the first of seven kings
• The Roman Republic, which commenced in 509 BC when kings were replaced with rule by elected magistrates. The period was marked by vast expansion of Roman territory. During the 5th century BC, Rome gained regional dominance in Latium. With the Punic Wars from 264 to 146 BC, ancient Rome gained dominance over the Western Mediterranean, displacing Carthage as the dominant regional power.
• The Roman Empire followed the Republic, which waned with the rise of Julius Caesar, and by all measures concluded after a period of civil war and the victory of Caesar's adopted son, Octavian, in 27 BC over Mark Antony.
• The Western Roman Empire collapsed in 476 after the city was conquered by the Ostrogothic Kingdom. Consequently, Rome's power declined, and it eventually became part of the Eastern Roman Empire, as the Duchy of Rome, from the 6th to 8th centuries. At this time, the city was reduced to a fraction of its former size, being sacked several times in the 5th to 6th centuries, even temporarily depopulated entirely.
• Medieval Rome is characterised by a break with Constantinople and the formation of the Papal States. The Papacy struggled to retain influence in the emerging Holy Roman Empire, and during the saeculum obscurum, the population of Rome fell to as low as 30,000 inhabitants. Following the East–West Schism and the limited success in the Investiture Controversy, the Papacy did gain considerable influence in the High Middle Ages, but with the Avignon Papacy and the Western Schism, the city of Rome was reduced to irrelevance, its population falling below 20,000. Rome's decline into complete irrelevance during the medieval period, with the associated lack of construction activity, assured the survival of very significant ancient Roman material remains in the centre of the city, some abandoned and others continuing in use.
• The Roman Renaissance occurred in the 15th century, when Rome replaced Florence as the centre of artistic and cultural influence. The Roman Renaissance was cut short abruptly with the devastation of the city in 1527, but the Papacy reasserted itself in the Counter-Reformation, and the city continued to flourish during the early modern period. Rome was annexed by Napoleon and was part of the First French Empire from 1809 to 1814.
• Modern history, the period from the 19th century to the present. Rome came under siege again after the Allied invasion of Italy and was bombed several times. It was declared an open city on 14 August 1943. Rome became the capital of the Italian Republic (established in 1946). With a population of 4.4 million (as of 2015; 2.9 million within city limits), it is the largest city in Italy. It is among the largest urban areas of the European Union and classified as a global city.

The Roman emperor was the ruler and monarchical head of state of the Roman Empire, starting with the granting of the title augustus to Octavian in 27 BC. The title of imperator, originally a military honorific, was usually used alongside caesar, originally a cognomen. When a given Roman is described as becoming emperor in English, it generally reflects his accession as augustus, and later as basileus. Early emperors also used the title princeps ("first one") alongside other Republican titles, notably consul and pontifex maximus.

The legitimacy of an emperor's rule depended on his control of the Roman army and recognition by the Senate; an emperor would normally be proclaimed by his troops, or by the Senate, or both. The first emperors reigned alone; later emperors would sometimes rule with co-emperors to secure the succession or to divide the administration of the empire between them. The office of emperor was thought to be distinct from that of a rex ("king"). Augustus, the first emperor, resolutely refused recognition as a monarch. For the first three hundred years of Roman emperors, efforts were made to portray the emperors as leaders of the Republic, fearing any association with the kings who ruled Rome prior to the Republic.