Julius Nepos (died 9 May 480), or simply Nepos, ruled as Roman emperor of the West from 24 June 474 to 28 August 475. After losing power in Italy, Nepos retreated to his home province of Dalmatia, from which he continued to claim the western imperial title, with recognition from the Eastern Roman Empire, until he was murdered in 480. Though Nepos' successor in Italy, Romulus Augustulus (r. 475–476), is traditionally deemed the last western Roman emperor, Nepos is regarded by some historians as the true last emperor of the west, being the last widely recognised claimant to the position.

A native of Dalmatia, Nepos began his career as the semi-autonomous governor of the province, succeeding his uncle Marcellinus, a prominent general, as magister militum ('master of troops') of Dalmatia. After the death of the western emperor Anthemius (r. 467–472), who had been appointed by the eastern emperor Leo I (r. 457–474), as well as Anthemius' successor Olybrius (r. 472), Leo sought to assert his authority in the west, granting Nepos command of an army in December 473 to attack Italy and depose Glycerius (r. 473–474), who had been proclaimed emperor by the Burgundian general Gundobad. Nepos left for Italy in the spring of 474, backed by Leo's successor Zeno, and landed with his army at Portus, near Rome. Nepos swiftly deposed Glycerius and was crowned western emperor in Rome on 24 June 474. He was the last emperor to be crowned in the city until Charlemagne in the ninth century. Whether the original intention of the invasion was to install Nepos as western emperor is unclear, but in any event, he was quickly recognised as the legitimate western emperor by Zeno.

Nepos worked to restore the prestige and authority of the Western Empire, though mostly unsuccessfully. He may have repelled a Visigothic attack on Italy and managed to once more reduce the Burgundians into foederati. Nepos focused most of his attention on reasserting imperial control and authority in Gaul, but the Western Empire could no longer project enough strength to halt Visigothic conquests in the region. The failure to defeat the Visigoths in Gaul, and Zeno's brief overthrowal in Constantinople by the usurper Basiliscus, weakened Nepos' already shaky position in Italy. In 475, Nepos' newly appointed magister militum Orestes revolted and marched on Ravenna, capital of the Western Empire. Unable to deal with Orestes' forces, Nepos fled back to Dalmatia and two months later, Orestes proclaimed his young son Romulus Augustulus as emperor.

Although no longer in control of Italy, Nepos never renounced his claim to the Western Empire and continued to be recognised as the legitimate western emperor by the Eastern Empire. In 476, the barbarian general Odoacer deposed Romulus Augustulus and became the first king of Italy. Nepos repeatedly petitioned Zeno, who by then had defeated Basiliscus, for help in regaining control of Italy, though all he achieved was nominal recognition by Odoacer, who minted coins in Nepos' name but otherwise mostly ignored him. In 480, Nepos was murdered by two of his generals, Ovida and Viator, perhaps in Diocletian's Palace, possibly while planning an expedition of his own to recover Italy.