Ercole Consalvi was a deacon and cardinal of the Catholic Church, who served twice as Cardinal Secretary of State for the Papal States and who played a crucial role in the post-Napoleonic reassertion of the legitimist principle of the divine right of kings, of which he was a constant supporter.

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.