Sergio Guerri (25 December 1905 – 15 March 1992) was an Italian Cardinal of the Roman Catholic Church who served as personal theologian to five popes from 1955 to 1989, and was elevated to the cardinalate in 1969.

On 9 March 1948, Guerri was named Pro-Secretary of the Administration of the Patrimony of the Holy See, becoming its full Secretary on 1 January 1951.

He was made Secretary of the Administration of the Patrimony of Holy See (7 May 1968) before becoming Pro-President of the Pontifical Commission for Vatican City State on 6 November 1968.

A close friend of Paolo Bertoli and Umberto Mozzoni, he remained in this post until he was succeeded in 1969 by Giuseppe Caprio.

He received his episcopal consecration on the following 27 April from Cardinal Amleto Giovanni Cicognani, with Bishops Joseph Mark McShea and Plinio Pascoli, serving as co-consecrators, in the chapel of the Lateran Seminary.