The Prosopographia Imperii Romani, abbreviated PIR, is a collective historical work to establish the prosopography of high-profile people from the Roman empire. The time period covered extends from the Battle of Actium in 31 BC to the reign of Diocletian. The final volume of the second edition, PIR², vol. IX, V–Z, appeared in November 2015.

The first edition was rapidly achieved and published in Berlin in the line of the great works of scholarship from the historical school of economics which had been successful in achieving the project of a corpus of all the Latin inscriptions, the Corpus inscriptionum latinarum. Led by Elimar Klebs, Hermann Dessau and Paul von Rohden,^[1] the first edition of the PIR was edited in three volumes from 1897 to 1898.

The implementation of a second edition was last updated in 1933 for publication in Berlin. The first booklet of the second edition was led by Edmund Groag and Arthur Stein^[1] who brought together the letters A and B. The publication was interrupted by World War II while working on the letter F (1943). From 1952 they took the direction of Stein and then Leiva Petersen. After German unification the project found a new dynamic. It was from then on led by K. Wachtel. The fascicle concerning the letter S was then published in 2006, and T in 2009. The index of names and people integral to the PIR was in the meantime made searchable on the website of the PIR.^[2]

Volume 2 of the PIR includes notes for all the well-known Roman senators, the nobles, and some civil servants not of equestrian rank, such as manumitted imperial freedmen who are attested in the literary tradition. Entries in the PIR are indexed by the initial letter of the name, then by the number of the entry, i.e. Tiberius Claudius Pompeianus corresponds to the entry PIR² C 973: the 973rd entry under the letter C.

For periods after the third century which the PIR does not cover, there is Prosopography of the Later Roman Empire by A.H.M. Jones, J.R. Martindale, and John Morris.^[1]