Postumius Titianus was a member of the third century ‘’gens Postumii’’, which was not descended from the Republican family of the same name.
[1] Around 291/292, Postumius Titianus was appointed corrector Transpadanae cognoscens vice sacra and electus ad iudicandas sacras appellationes (that is, the Corrector of Cisalpine Gaul and the officer responsible for the management of imperial judicial duties and the execution of the emperor's will).
[2] This was followed in 293/294 or 294/295 by his posting as consularis aquarum et Miniciae (or the official with proconsular imperium responsible for maintaining the aqueducts and grain importation into Rome).
He employed a Titus Aelius Poemenius as his assistant, who set up an inscription to Postumius Titianus when he completed his posting.
Finally, he was appointed Praefectus urbi of Rome, a position he held from 12 February 305 to 19 March 306.