Nepos fled to Dalmatia and continued to claim the imperial title in exile, which hampered Romulus's legitimacy and ensured that he was never recognised by the Eastern Roman emperor Zeno.

After various divisions were made throughout the 4th century, the empire was firmly and permanently divided into a western and eastern sphere of imperial administration from the death of emperor Theodosius I (r. 379–395) in 395 onwards.

[9] In 410, the Visigoths under Alaric I had sacked Rome and in 455, the last western emperor of Theodosius' dynasty, Valentinian III (r. 425–455), was deposed and murdered.

In 475, Nepos named Orestes as a patrician and magister militum ('master of soldiers'; effectively commander-in-chief), replacing the previous holder of that office, Ecdicius.

[1] As magister militum, Orestes was tasked by Nepos to lead an army against Visigoths and Burgundians, foederati (barbarian allies of the empire) who were rebelling in southern Gaul.

Obeying to the grievances of his troops, among other things learning that Nepos had refused requests for land grants,[13] Orestes betrayed the emperor's orders and marched on Ravenna, the capital of the western empire.

[1][14][13] There is little surviving concrete evidence in regards to Romulus' ancestry beyond Orestes being known to have been a Roman citizen from Pannonia and sparse information on his immediate family.

[16] After an interregnum in the west lasting two months, Romulus, perhaps as young as ten years old,[3] was proclaimed emperor in Nepos' stead by Orestes on 31 October 475.

[14] Why the interregnum since Nepos lasted so long and why Orestes, a high-ranking military official and a Roman by birth, did not take the imperial title for himself is not known.

[1] Romulus would throughout his brief ten-month reign be little more than a figurehead, with his father, who retained the position of magister militum, actually running much of the imperial administration.

[3] According to the 5th-century Eastern Roman writer and historian Malchus, Odoacer may have forced Romulus himself, as his last official act as emperor, to send the imperial regalia and a "letter of resignation" to Zeno, writing that the Roman Empire from this point only required a single emperor, ruling from Constantinople.

Though Zeno granted Odoacer the distinction of patrician, he also urged the king to accept Julius Nepos back as emperor in Italy.

[7] Romulus was granted an annual pension of 6,000 solidi (the normal income of a wealthy Roman senator) and granted an estate in Campania near Naples called the castellum Lucullanum (today called Castel dell'Ovo), originally built by the consul and general Lucius Licinius Lucullus in the 60s BC.

[3] Romulus may have played a role in founding a monastery around the remains of Saint Severinus of Noricum at castellum Lucullanum in the 480s or early 490s.

The scant narrative record and few known coins, in addition to there not being any known inscriptions of significance or laws issued by the emperor, make him a shadowy and relatively inconsequential figure.

In The History of the Decline and Fall of the Roman Empire (1776–1788), Edward Gibbon wrote that he "assumed and disgraced the names of Romulus [and] Augustus".

In The History of the Decline and Fall of the Roman Empire, Gibbon wrote that "the appellations of the two great founders of the city and of the monarchy were thus strangely united in the last of their successors".

[3] In particular, some historians, such as Ralph W. Mathisen and Marjeta Šašel Kos, have pointed to Julius Nepos as the actual last Western Roman emperor.

Though he never regained Italy, Nepos continued to rule in Dalmatia, with support from Zeno and with nominal recognition by Odoacer, until he was murdered in 480.

[28] In Visigothic Hispania, two Roman usurpers rose from the Ebro valley, attempting to claim imperial authority: Burdunellus (496) and Petrus (506).

[29][30] Romulus Augustus being identified as the last emperor of the western empire is a tradition that began already among eastern Roman historians and writers in the early 6th century.

The earliest known writer to consider him as such was Marcellinus Comes (died c. 534), who wrote the following passage concerning Romulus:[1] The western Empire of the Roman people, which first began in the seven hundred and ninth year after the founding of the City with Octavian Augustus, the first of the emperors, perished with this Augustulus, in the five-hundred and twenty-second year of the reign of Augustus' successor emperors.