As the Abasgi grew in relative strength, the name Abasgia came to denote a larger area populated by various ethnic groups including Mingrelian- and Svan-speaking South Caucasian tribes, and subordinated to the Byzantine-appointed princes (Greek: archon, Georgian: eristavi) who resided in Anacopia and were viewed as major champions of the empire’s political and cultural influence in the western Caucasus. The Arabs penetrated the area in the 730s, but did not subdue it; about then the term Abkhazeti ("the land of the Abkhazians") first appeared in the Georgian annals, giving rise to the name Abkhazia, which is used today in most foreign languages.
Through their dynastic intermarriages and alliance with other Georgian princes, the Abasgian dynasty acquired most of Lazica/Egrisi, and in the person of Leo established themselves as "kings of the Abkhazians" in the 780s. With the Khazar help, Leo ousted the Byzantines and expanded his kingdom, transferring his capital to the Georgian city of Kutaisi. Although the nature of this kingdom's ruling family is still disputed, most scholars agree that the Abkhazian kings were Georgian in culture and language. In order to eliminate the Byzantine religious influence, the dynasty subordinated the local dioceses to the Georgian Orthodox patriarchate of Mtskheta.
The kingdom is frequently referred in modern history writing as the Egrisi-Abkhazian kingdom due to the fact that medieval authors viwed the new monarchy as a successor state of Egrisi and sometimes used the terms interchangeably.
The most prosperous period of the Abkhazian kingdom was between 850 and 950, when it dominated the whole western Georgia and claimed control even of the easternmost Georgian provinces. The terms "Abkhazia" and "Abkhazians" were used in a broad sense during this period – and for some while later – and covered, for all practical purposes, all the population of the kingdom regardless of their ethnicity.}} In 989, the Bagratid ruler Bagrat III came to power in Abkhazia which he inherited from his mother Guranduxt Anch'abadze. In 1008 Bagrat inherited K'art'li from his father and united the kingdoms of Abkhazia and Georgia into a single Georgian feudal state.
This state reached the apex of its strength and prestige under the queen Tamar (1184-1213). On one occasion, a contemporary Georgian chronicler mentions a people called Apsars. This source explains the sobriquet 'Lasha' of Tamar's son and successor George IV as meaning "enlightenment" in the language of the Apsars. Some modern linguists link this nickname to the modern Abkhaz words a-lasha for "clear" and a-lashara for "light", identifying the Apsars with the possible ancestors of the modern-day Abkhaz, though the exact identity and location of this tribe is unclear.
Bagrat III of Georgia; of the House of BagrationiAccording to the Georgian chronicles, Queen Tamar granted the lordship over part of Abkhazia to the Georgian princely family of Shervashidze. According to traditional accounts, they were an offshoot of the Shirvanshahs (hence allegedly comes their dynastic name meaning "sons of Shirvanese" in Georgian). The ascendancy of this dynasty (later known also as Chachba by the Abkhaz form of their surname) in Abkhazia would last until the Russian annexation in the 1860s.
The Genoese established their trading factories along the Abkhazian coastline in the 14th century, but they functioned for a short time. The area was relatively spared from the Mongol and Timur's invasions, which terminated Georgia's "golden age". As a result, the kingdom of Georgia fragmentized into several independent or semi-independent entities by the late 15th century. The Principality of Abkhazia was one of them. The Abkhazian princes engaged in incessant conflicts with the Mingrelian potentates, their nominal suzerains, and the borders of both principalities fluctuated in the course of these wars. In the following centuries, the Abkhazian nobles finally prevailed and expanded their possessions up to the Inguri River, which is today's southern boundary of the region. Several medieval historians like Vakhushti and a few modern ones claimed that the Kelasuri Wall was built by prince Levan II Dadiani of Mingrelia as a protection against Abkhaz.