Why is Pope Gregory I known as St. Gregory the Great?

Pope Gregory I is known as St. Gregory the Great because of his significant contributions as both a ruler and a writer, which established him as the founder of the medieval papacy.12

His epithet reflects his multifaceted legacy:

• Administrative Reformer: As pope from 590 to 604, he was an excellent administrator who "monasticized" the papal government by replacing entrenched clergy with monks and trusted associates. He focused on justice and charity, famously referring to himself as the "servant of the servants of God".123
• Secular and Spiritual Leader: During a period of instability, he exercised both secular and spiritual power, directing diplomacy, funding soldiers, and orchestrating policies to protect Rome from the Lombards.14
• Intellectual Legacy: He is recognized as the fourth and final of the traditional Latin Fathers of the church and was a primary exponent of medieval, sacramental spirituality.1

Additionally, his influence extended to the conversion of England, leading to his recognition as the "Apostle of the English" for organizing the mission of St. Augustine of Canterbury.35