Giovanni Benelli received his education in the seminary of Pistoia and at two universities in Rome. In 1943 he received the sacrament of Holy Orders and was then seven years used as a church pastor in the Diocese of Rome. After further studies, he joined in 1947 in the service of the Vatican Secretariat of State, where he was personal secretary to Giovanni Battista Montini, the future Pope Paul VI. Was. 1950 Pope Pius XII appointed him. Secretary of the Apostolic Nunciature in Ireland. Further stations of his diplomatic career took him from 1953 to 1960 in France and 1960 to 1962 in Brazil. From 1962 to 1965 he worked as a consultant to the Apostolic Nunciature in Spain, in the years 1965 and 1966 he was a permanent observer of the Holy See at UNESCO in Paris.
1966 Pope Paul VI appointed him. Titular Archbishop of Tusuros and Apostolic Pro-Nuncio to Senegal as well as apostolic envoy for West Africa. He received his episcopal consecration on 11 September 1966, the then Cardinal Secretary of State, Cardinal Cicognani Amleto Giovanni.
In 1967 he returned to the Vatican Secretariat of State. Under Secretary of State Cardinal Jean -Marie Villot him grew from 1969 as a substitute a great abundance of power to who used the dynamic multi workers massively. Among other things, he influenced Catholicism in Spain, a gradual end to the system Franco perform. Influenced Christian- democratic, Benelli was also in marked contrast to the French traditionalism. Inside the church the political spectrum in Italy Benelli was considered moderate progressive.
As a favorite of the aging Pope Giovanni Benelli 1977, he received the appointment as Archbishop of Florence, and was accepted as a cardinal priest with the titular church of Santa Prisca in the College of Cardinals on 27 June 1977. In the two conclaves of 1978, he was indeed a promising candidate there, worked initially but campaigning in favor of Cardinal Luciani ( John Paul I ) and in the October election of John Paul II Cardinal Benelli died on October 26, 1982 after a sudden heart attack in Florence and was buried in the local Metropolitan Basilica. He was only 61 years old.