How many Roman emperors were there (in total)?

Depends on what you count as Roman emperor. If you count only the unified empire rulers, there were 71 emperors and co-regents from Augustus to Theodosius. The Unified Empire broke up finally in 395 AD. If you count the Western Empire rulers (395 to 479, from Honorius to Romulus Augustulus) there were 16 more emperors and co-regents. read more

Any individual who was nominated as heir or co-emperor by a legitimate emperor (1), and who succeeded to rule in his own right, is a legitimate emperor (2). Where there were multiple claimants, and none were legitimate heirs, the claimant accepted by the Roman Senate as emperor is the legitimate emperor (3), at least during the Principate. read more