The Augustan History (Latin: Historia Augusta) is a late Roman collection of biographies, in Latin, of the Roman Emperors, their junior colleagues, designated heirs and usurpers of the period 117 to 284. Supposedly modelled on the works of Suetonius, it presents itself as a compilation of works by six different authors (collectively known as the Scriptores Historiae Augustae), written during the reigns of Diocletian and Constantine I and addressed to those emperors or other important personages in Rome. The collection, as extant, comprises thirty biographies, most of which contain the life of a single emperor, while some include a group of two or more, grouped together merely because these emperors were either similiar or contemporaneous.