Sextus Varius Marcellus is a Roman of equestris class, but is later elevated to the rank of senator.

Although he has little administrative experience he is related to Septimius Severus and the new emperor sends him to Roman Britain in 197 to assist Virius Lupus in rebuilding the province.

Marcellus serves as provincial procurator, collecting taxes, generally managing Britain's finances and possibly overseeing the appropriation of private land to the emperor's res privata.

He marries Julia Soaemias, and is the supposed father of Varius Avitus Bassianus, the later Roman Emperor Marcus Aurelius Antoninus, better known as Elagabalus.