Which Pope established the authority of the office of Pope in the 6th century?

The significant figure associated with establishing the authority of the office of Pope in the 6th century is Gregory I, commonly known as Pope Gregory the Great. He assumed papal leadership around 590 AD and is notable for asserting the spiritual and temporal authority of the papacy during a time when the Roman Empire was in decline and faced challenges from various external and internal forces.

Gregory’s papacy marked a pivotal moment in the Church's consolidation of power. He reinforced the role of the Pope as the supreme leader of the Christian Church and emphasized the Pope's role as a mediator between God and humanity. Gregory also took significant steps to organize the Church, manage its resources, and promote missionary work, thereby extending the influence of the papacy beyond Italy.

His contributions to Church doctrine and administration had a lasting impact, leading to increased papal authority that would shape the future of the church and Western Christendom. This development was crucial in positioning the Pope not only as a religious leader but also as a key political figure in medieval Europe.