Justin I (10 July 518 - 1 August 527). Flavius Iustinus Augustus was a career soldier and illiterate, but became emperor at an advanced age due to chance. He was the founder of the Justinian Dynasty. During his reign, most of the imperial policies were formulated by his brilliant nephew, Justinian. He formally named Justinian co-emperor in 526, and named him his successor on April 1, 527.