Flavius Petrus Sabbatius Justinianus, commonly known as Justinian I, was a Byzantine emperor who ruled from 527 to 565 AD. He is known for his efforts to restore the Roman Empire and his ambitious building projects, including the construction of the Hagia Sophia. Justinian is also remembered for his legal reforms, particularly the codification of Roman law in the Corpus Juris Civilis, which had a lasting impact on legal systems in Europe. His reign was marked by military campaigns to reclaim lost territories and his efforts to strengthen the Byzantine Empire's influence in the Mediterranean region.