Tamar was proclaimed heir and co-ruler by her reigning father George III in 1178, but she faced significant opposition from the aristocracy upon her ascension to full ruling powers after George's death. Tamar was successful in neutralizing this opposition and embarked on an energetic foreign policy aided by the decline of the hostile Seljuq Turks. Relying on a powerful military élite, Tamar was able to build on the successes of her predecessors to consolidate an empire which dominated the Caucasus until its collapse under the Mongol attacks within two decades after Tamar's death.
Tamar was married twice, her first union being, from 1185 to 1187, to the Rus' prince Yuri, whom she divorced and expelled from the country, defeating his subsequent coup attempts. For her second husband Tamar chose, in 1191, the Alan prince David Soslan, by whom she had two children, George and Rusudan, the two successive monarchs on the throne of Georgia.
Tamar's association with the period of political and military successes and cultural achievements, combined with her role as a female ruler, has led to her idealization and romanticization in Georgian arts and historical memory. She remains an important symbol in Georgian popular culture and has been canonized by the Georgian Orthodox Church as the Holy Righteous Queen Tamar (წმიდა კეთილმსახური მეფე თამარი, ts'mida k'etilmsakhuri mepe tamari), with her feast day commemorated on 14 May (O.S. 1 May).
Tamar was born in circa 1160 to George III, King of Georgia, and his consort Burdukhan, a daughter of the king of Alania. While it is possible that Tamar had a younger sister, Rusudan, she is only mentioned once in all contemporary accounts of Tamar's reign. The name Tamar is of Hebrew origin and, like other biblical names, was favored by the Georgian Bagrationi dynasty because of their claim to be descended from David, the second king of Israel.
Tamar's youth coincided with a major upheaval in Georgia; in 1177, her father, George III, was confronted by a rebellious faction of nobles. The rebels intended to dethrone George in favor of the king's fraternal nephew, Demna, who was considered by many to be a legitimate royal heir of his murdered father, David V. Demna's cause was little but a pretext for the nobles, led by the pretender's father-in-law, the amirspasalar ("high constable") Ivane Orbeli, to weaken the crown. George III was able to crush the revolt and embarked on a crackdown campaign on the defiant aristocratic clans; Ivane Orbeli was put to death and the surviving members of his family were driven out of Georgia. Prince Demna, castrated and blinded on his uncle's order, did not survive the mutilation and soon died in prison. Once the rebellion was suppressed and the pretender eliminated, George went ahead to co-opt Tamar into government with him and crowned her as co-ruler in 1178. By doing so, the king attempted to preempt any dispute after his death and legitimize his line on the throne of Georgia. At the same time, he raised men from the gentry and unranked classes to keep the dynastic aristocracy away from the center of power.
For six years, Tamar was a co-ruler with her father upon whose death, in 1184, Tamar continued as the sole monarch and was crowned a second time at the Gelati cathedral near Kutaisi, western Georgia. She inherited a relatively strong kingdom, but the centrifugal tendencies fostered by the great nobles were far from being quelled. There was considerable opposition to Tamar's succession; this was sparked by a reaction against the repressive policies of her father and encouraged by the new sovereign's other perceived weakness, her sex. As Georgia had never previously had a female ruler, a part of the aristocracy questioned Tamar's legitimacy, while others tried to exploit her youth and supposed weakness to assert greater autonomy for themselves. The energetic involvement of Tamar's influential aunt Rusudan and the Catholicos-Patriarch Michael IV was crucial for legitimizing Tamar's succession to the throne. However, the young queen was forced into making significant concessions to the aristocracy. She had to reward the Catholicos-Patriarch Michael's support by making him a chancellor, thus placing him at the top of both the clerical and secular hierarchies.
Tamar was also pressured into dismissing her father's appointees, among them the constable Kubasar, a Georgian Kipchak of ignoble birth, who had helped George III in his crackdown on the defiant nobility. One of the few untitled servitors of George III to escape this fate was the treasurer Qutlu Arslan who now led a group of nobles and wealthy citizens in a struggle to limit the royal authority by creating a new council, karavi, whose members would alone deliberate and decide policy. This attempt at "feudal constitutionalism" was rendered abortive when Tamar had Qutlu Arslan arrested and his supporters were inveigled into submission. Yet, Tamar's first moves to reduce the power of the aristocratic élite were unsuccessful. She failed in her attempt to use a church synod to dismiss the Catholicos-Patriarch Michael, and the noble council, Darbazi, asserted the right to approve royal decrees.