Agostino Casaroli was an Italian Catholic priest and diplomat for the Holy See, who became Cardinal Secretary of State. He was an important figure behind the Vatican's efforts to deal with the religious persecution of the Church in the nations of the Soviet bloc after the Second Vatican Council.

The Secretary of State of His Holiness, known as the Cardinal Secretary of State, presides over the Holy See's Secretariat of State, which is the oldest and most important dicastery of the Roman Curia. The Secretariat of State performs all the political and diplomatic functions of the Holy See and the Vatican City State. The secretary of state is sometimes described as the prime minister of the Holy See, even though the nominal head of government of Vatican City is the President of the Pontifical Commission for Vatican City State.