Massimo Massimi was an Italian cardinal of the Roman Catholic Church who served as Prefect of the Apostolic Signatura in the Roman Curia from 1946 until his death, and was elevated to the cardinalate in 1935.

The papal conclave held on 1 and 2 March 1939 saw Cardinal Eugenio Pacelli elected on the third ballot to succeed Pius XI, who had died on 10 February, as pope. All 62 cardinals took part. Pacelli, who had been camerlengo and secretary of state, took the name Pius XII. The day was his 63rd birthday.