Aurelius/Iulius Marcellinus (his nomen is uncertain) was a Roman soldier and Imperial functionary who had a brilliant equestrian career and was elevated to the Senate when he was chosen by the Emperor Aurelian as his consular colleague. His appointment as Consul is thought to have been a reward for his loyalty and steadfastness in 273 when, as Aurelian's deputy in charge of the eastern provinces of the Empire where the authority of the Imperial Government had only recently been restored, he resisted attempts to suborn him by a rebellious faction in the city of Palmyra.

His promotion was unusual in that he had not achieved the rank of Praetorian Prefect, the level of seniority in the Imperial Service at which equestrian officials might hope to be elevated to the Senate. However, this practice, which was to become a regular feature during the reign of Diocletian, was still inchoate in 275 AD.

Obviously a man of considerable capabilities who had attracted the Imperial patronage of Emperor Gallienus and whose services continued to be much valued by Aurelian, the paucity of the surviving records means that even the identity of Marcellinus is uncertain while nothing else is known of his life beyond the bare outlines recounted here.

There is no record of Marcellinus's origins or early life.

Scholarly opinion is in agreement that the first reference to Marcellinus is from an inscription that places him in Verona around 265 AD. However, the matter of his identity is complicated by the fact that his consular reference does not include a nomen while the Verona inscription names two Marcellini either of whom may have been the Consul Posterior of 275 AD.

The first Marcellinus referred to in this inscription by order of seniority had the nomen Aurelius. He is described as a Vir Perfectissimus and a dux - in other words, a senior officer carrying out a specific commission for the ruling Emperor (Gallienus). His task in Verona was to fortify the city.

The second Marcellinus referred to in the Verona inscription had the nomen Iulius, and his status was Vir Egregius. He was probably a serving soldier. His rank is not indicated, but he may have been either a tribunus or a praefectus legionis. He was associated with the fortification of Verona and he may have served under Aurelius Marcellinus.

The fortification of Verona formed part of an extensive series of defensive works around and within Italy undertaken by Gallienus in the wake of the barbarian assaults of the later-250s. They were begun in April of the year in which Valerian, the brother of the Gallienus, was consul for the second time with Lucilius as his posterior - i.e. 265 AD - and were finished in September.