In stark contrast to the catastrophic collapse of the Western Roman Empire, the Eastern Roman Empire (frequently called the Byzantine Empire by modern historians) survived the 5th century more or less intact and its predominantly Greek-speaking population continued to identify themselves as Romans (Rhomaioi), as they remained inhabitants of the Roman Empire.
The name Romania ("land of the Romans"), a later popular designation by the people of the Byzantine Empire for their country, is attested as early as 582 when it was used by the inhabitants of the city of Sirmium for their country.
Although rarely expressed as an idea before the 9th century, the earliest mention of the Byzantine Empire as being "Greek" is from the 6th century, written by Bishop Avitus of Vienne in the context of the Frankish king Clovis I's baptism; "Let Greece, to be sure, rejoice in having an orthodox ruler, but she is no longer the only one to deserve such a great gift".
To the early Byzantines (up until around the 11th century) the term "Greeks" or "Hellenes" was offensive as it downplayed their Roman nature and furthermore associated them with the ancient Pagan Greeks rather than the more recent Christian Romans.

The idea of the res publica remained an important imperial concept for centuries.
In the Frankish king Childebert II's letters to Emperor Maurice, the emperor is called the princeps Romanae reipublicae and through the 6th and 8th centuries, terms such as res publica and sancta res publica was still sometimes applied to the Byzantine Empire by authors in Western Europe.
This practice only ceased as Byzantine control over Italy and Rome itself crumbled and "Roman" as a name and concept became more heavily associated by Western authors with the city itself.
The use of the term Romani was somewhat similar, usually often used in reference to the inhabitants of the Byzantine Empire by early Medieval western authors when not used for the population of the city itself.
In Isidore of Seville's History of the Goths, the term Romani refers to the Byzantine Empire and their remaining garrisons in Spain and the term is never applied to the population of the former western provinces.

References to the Romans as a gens, like the Barbarian gentes, begin to appear around the time of Justinian's conquests.
Priscian, a grammarian who was born in Roman North Africa and later lived in Constantinople during the late 5th century and early 6th century, refers in his work to the existence of a gens Romana.
Letters written by the Frankish king Childebert II to Emperor Maurice in Constantinople in the 580s talk of the peace between the two "gentes of the Franks and the Romans".
The 6th century historian Jordanes, himself identifying as a Roman, refers to the existence of a Roman gens in the title of his work on Roman history, De summa temporum vel de origine actibusque gentis Romanorum.
The idea of Romans as a gens like any other didn't become generally accepted in the East until the 11th century.
For instance, Emperor Basil I (r. 867–886) still considered "Roman" to be an identity that was defined as an opposite to being of a Barbarian gens.
Before the 11th century, the "Romans" discussed in Byzantine texts usually refer to individuals loyal to the Byzantine emperor who followed Chalcedonian Christianity.
As such, the Romans were all the Christian subjects of the emperor.

In the 27th chapter of Emperor Constantine VII's 10th century political treatise De Administrando Imperio, the emperor expressed the idea that the Imperium had been transferred from Rome to Constantinople once Rome stopped being ruled by an emperor.
The 12th century historian John Kinnamos expresses similar views, seeing the rights to the imperium as having disappeared from Rome and the west since power passed there from the last Western Roman emperors to Barbarian kings who had no claim to being Roman.
As such, the ruler in Constantinople was the sole ruler in Europe who could claim to be a true Roman.
As such, the transfer of power from Rome to Constantinople that had begun under Constantine
In stark contrast to the catastrophic collapse of the Western Roman Empire, the Eastern Roman Empire (frequently called the Byzantine Empire by modern historians) survived the 5th century more or less intact and its predominantly Greek-speaking population continued to identify themselves as Romans (Rhomaioi), as they remained inhabitants of the Roman Empire. The name Romania ("land of the Romans"), a later popular designation by the people of the Byzantine Empire for their country, is attested as early as 582 when it was used by the inhabitants of the city of Sirmium for their country. Although rarely expressed as an idea before the 9th century, the earliest mention of the Byzantine Empire as being "Greek" is from the 6th century, written by Bishop Avitus of Vienne in the context of the Frankish king Clovis I's baptism; "Let Greece, to be sure, rejoice in having an orthodox ruler, but she is no longer the only one to deserve such a great gift". To the early Byzantines (up until around the 11th century) the term "Greeks" or "Hellenes" was offensive as it downplayed their Roman nature and furthermore associated them with the ancient Pagan Greeks rather than the more recent Christian Romans.
The idea of the res publica remained an important imperial concept for centuries. In the Frankish king Childebert II's letters to Emperor Maurice, the emperor is called the princeps Romanae reipublicae and through the 6th and 8th centuries, terms such as res publica and sancta res publica was still sometimes applied to the Byzantine Empire by authors in Western Europe. This practice only ceased as Byzantine control over Italy and Rome itself crumbled and "Roman" as a name and concept became more heavily associated by Western authors with the city itself. The use of the term Romani was somewhat similar, usually often used in reference to the inhabitants of the Byzantine Empire by early Medieval western authors when not used for the population of the city itself. In Isidore of Seville's History of the Goths, the term Romani refers to the Byzantine Empire and their remaining garrisons in Spain and the term is never applied to the population of the former western provinces.
References to the Romans as a gens, like the Barbarian gentes, begin to appear around the time of Justinian's conquests. Priscian, a grammarian who was born in Roman North Africa and later lived in Constantinople during the late 5th century and early 6th century, refers in his work to the existence of a gens Romana. Letters written by the Frankish king Childebert II to Emperor Maurice in Constantinople in the 580s talk of the peace between the two "gentes of the Franks and the Romans". The 6th century historian Jordanes, himself identifying as a Roman, refers to the existence of a Roman gens in the title of his work on Roman history, De summa temporum vel de origine actibusque gentis Romanorum. The idea of Romans as a gens like any other didn't become generally accepted in the East until the 11th century. For instance, Emperor Basil I (r. 867–886) still considered "Roman" to be an identity that was defined as an opposite to being of a Barbarian gens. Before the 11th century, the "Romans" discussed in Byzantine texts usually refer to individuals loyal to the Byzantine emperor who followed Chalcedonian Christianity. As such, the Romans were all the Christian subjects of the emperor.
In the 27th chapter of Emperor Constantine VII's 10th century political treatise De Administrando Imperio, the emperor expressed the idea that the Imperium had been transferred from Rome to Constantinople once Rome stopped being ruled by an emperor. The 12th century historian John Kinnamos expresses similar views, seeing the rights to the imperium as having disappeared from Rome and the west since power passed there from the last Western Roman emperors to Barbarian kings who had no claim to being Roman. As such, the ruler in Constantinople was the sole ruler in Europe who could claim to be a true Roman. As such, the transfer of power from Rome to Constantinople that had begun under Constantine 
Roman people