Gregory was born around 329 near Nazianzus in Cappadocia, the son of a local bishop of the same name, and studied rhetoric at Athens, where he formed a close friendship with a fellow student named Basil, later Basil the Great, a bond both men described in terms usually reserved for philosophical ideals of friendship. Gregory returned home wanting a quiet life of study and asceticism, but his father, then an elderly bishop, ordained him a priest against his wishes in 361, prompting Gregory to flee temporarily to join Basil at his monastic retreat before returning to help his father.
Basil, once he became Bishop of Caesarea, ordained Gregory bishop of the obscure town of Sasima in 372, a political move to secure the territory against a rival bishop, a task Gregory resented so much that he apparently never took up residence there at all, a strain that cooled but did not end the two men's friendship.
In 379 the small Nicene community of Constantinople, a city that had been under Arian control for decades, invited Gregory to lead them, and he arrived to a hostile city, preaching from a private house chapel he called Anastasia, resurrection, because it was there, he said, that Nicene faith in the capital was raised from the dead.