Gregory's origins are a matter for scholarly dispute. He is believed to have hailed from the region of Tao or Tayk, which had been ruled by Georgian Bagratids of kouropalatate of Iberia, later annexed by the Byzantines to the theme of Iberia in 1001. According to the contemporary historian Anna Comnena, who knew Pakourianos personally, Gregory was "descended from a noble Armenian family," while the Armenian chronicler Matthew of Edessa, from the 12th century, notes that he was of Georgian origin had in mind Pakourianos' religious affiliation. Gregory himself proclaimed that he belonged to "the glorious people of the Iberians" and insisted his monks to know the Georgian language. In her study on Byzantine administration over the provinces of Armenia, Armenian historian Viada Arutjunova-Fidanjan believes that Pakourianos was born into a Chalcedonian Armenian family. Taking into account all the evidence available on Pakourianos, the scholar Nina G. Garsoïan proposed that "the most likely explanation is that belonged to the mixed Armeno-Iberian Chalcedonian aristocracy, which dwelt in the border district of Tayk/Tao." According to Anna Comnena, Pakourianos was tiny of body but a mighty warrior.
Byzantine service
Since 1060 Gregory served in Byzantine army. In 1064 he had achieved a significant position among the Byzantine military aristocracy, but failed at defending Ani against the Seljuk leader Alp Arslan, King Bagrat IV of Georgia and Albanian King Goridzhan in the same year. Since 1071 he was appointed as a Strategos of the theme of Iberia. As the Seljuk advance forced the Byzantines to evacuate the eastern Anatolian fortresses and the theme of Iberia, Gregory ceded control over Kars and Tao to King George II of Georgia in 1074. This did not help, however, to stem the Turkish advance and the area became a battleground of the Georgian-Seljuk wars. Afterwards he served under Michael VII Doukas and Nikephoros III Botaneiates in various responsible positions on both the eastern and the western frontiers of the empire. Later Gregory was involved in a coup that removed Nikephoros III. The new Emperor, Alexios I Komnenos, appointed him "megas domestikos of All the West" and gave him many more properties in the Balkans. He possessed numerous estates in various parts of the Byzantine Empire and was afforded a variety of privileges by the emperor, including exemption from certain taxes. In 1081, he commanded the left flank against the Normans at the Battle of Dyrrachium. A year later he evicted the Normans from Moglena. He died in 1086 fighting the Pechenegs at the battle of Beliatoba, charging so vigorously he crashed into a tree. Gregory was also known as a noted patron and promoter of Christian culture. He together with his brother Abas made, in 1074, a significant donation to the Eastern OrthodoxHoly Monastery of Iviron on Mount Athos and commissioned the regulations for this foundation. He signed the Greek version of the Typikon in Armenian. He also signed his name in Georgian and Armenian characters rather than Greek. It is assumed that Pakourianos did not know Greek. Gregory Pakourianos and his brother Abas were buried in a bone-vault house near the Bachkovo Monastery. The portraits of the two brothers are painted on the north wall of the bone-vault house.
