Roman Italy was created officially by the Roman emperor Augustus with the Latin name Italia. It was the first time in history that the Italian Peninsula (from the Alps to the Ionian Sea) was united under the same name. In the year 292, the three islands of Corsica, Sardinia and Sicily (including Malta) were added to Roman Italy by Diocletian. Roman Italy remained united until the sixth century, when it was divided between the Byzantine Empire and territories of the Germanic peoples. Since then, "Italia" remained divided for nearly thirteen centuries until 1861 when it was reunited in a similar way in the modern "Kingdom of Italy".
Italy (Italia in Latin) was the name of the administrative division of the Italian Peninsula during the Roman era. It was not a province, but became the territory of the city of Rome, thus having a special status. Following the end of the Social War (91–88 BC), Rome had allowed its Italian allies (socii) full rights in Roman society and granted the Roman citizenship to all the Italic peoples.
After having been for centuries the heart of the Empire, from the 3rd century the government and the cultural center began to move eastward: first the Edict of Caracalla in 212 AD extended Roman citizenship to all free men within the imperial boundaries, then Christianity became the dominant religion during Constantine's reign (306–337) raising the power of other Eastern political centres. Although not founded as a capital city in 330, Constantinople gained in importance. It finally gained the rank of eastern capital when given an urban prefect in 359 and the senators who were clari became senators of the lowest rank as clarissimi.