Giovanni Battista Agucchi was an Italian churchman, Papal diplomat and writer on art theory. He was the nephew and brother of cardinals, and might have been one himself if he had lived longer. He served as secretary to the Papal Secretary of State, then the Pope himself, on whose death Agucchi was made a titular bishop and appointed as nuncio to Venice.

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.