Justinian I: Emperor of the Eastern Roman / Byzantine Empire
Born AD482, Died AD565
Justinian was Thracian born, coming from the area of modern Bulgaria and almost certainly growing up speaking that ancient language, though he would have undoubtably have thought of himself as Roman; the remenants of the native population of the area still refer to themselves as Romani. There is little firm evidence about Justinian's early career, he only comes into the historical limelight in AD518 when his Uncle Justin seized control of the Eastern Empire and raised Justinian to Patrician class with the rather amusing (to modern eyes) title of Count of Domestics, actualy a key and powerful position. It appears that Justinian became first his uncle's right hand man and then the power behind the throne, guiding all points of policy and legislation.
Justinian took over the throne after his uncle's death and imediately set about healing the long standing rift between the eastern and western churches, sending numerous letters to the Patriach of Rome aka the Pope culminating in the official reuniting of the two churches. Justinian married Theodora in around AD520, a match that (some might say unusually for heads of state) seems to have been a marrage of love.
Justinian is perhaps best remembered for his cataloguing of the laws of the Roman Empire. This was published in a number of parts; the Codex (1st ed in 529, revised and expanded in 534), the Digest in 530 covering the writings of Roman jurists, and the last part the Institutes, essentially a selection of the more significant laws from the other two volumes.
Justinians other major claim to fame is the reconquest of just about the whole Mediterranean coast. Admittedly it these campaigns cost a staggering fortune and the weren't held long after his death, but that is one hell of an acheivement none the less.