Roman emperor

The Roman emperor was the ruler and monarchical head of state of the Roman Empire, starting with the granting of the title augustus to Octavian in 27 BC. The title of imperator, originally a military honorific, was usually used alongside caesar, originally a cognomen. When a given Roman is described as becoming emperor in English, it generally reflects his accession as augustus, and later as basileus. Early emperors also used the title princeps ("first one") alongside other Republican titles, notably consul and pontifex maximus.

The legitimacy of an emperor's rule depended on his control of the Roman army and recognition by the Senate; an emperor would normally be proclaimed by his troops, by the Senate, or both. The first emperors reigned alone; later emperors would sometimes rule with co-emperors to secure the succession or to divide the administration of the empire between them. The office of emperor was thought to be distinct from that of a rex ("king"). Augustus, the first emperor, resolutely refused recognition as a monarch. For the first three hundred years of Roman emperors, efforts were made to portray the emperors as leaders of the Republic, fearing any association with the kings who ruled Rome prior to the Republic.