Mario Fiorentini (7 November 1918 – 9 August 2022) was an Italian partisan, spy, mathematician, and academic, for years a professor of geometry at the University of Ferrara. He engaged in numerous partisan actions, including the assault on the entrance to the Regina Coeli prison and participating in the organization of the Via Rasella attack. He was Italy's most decorated World War II partisan.

Fiorentini was born in Rome to Maria Moscatelli and Pacifico Fiorentini on 7 November 1918. His mother, a Catholic, moved to Rome from Cittaducale in search of work, like many other young people at the time; his father, who was Jewish, worked as an accountant and bankruptcy trustee.

As a student, Fiorentini collaborated clandestinely with Giustizia e Libertà and with the Communist Party. At the beginning of 1943, he set up with Plinio De Martiis [it] performances at Mazzini Theater and at Delle Arti with actors such as Vittorio Gassman, Lea Padovani, Nora Ricci, Vittorio Caprioli, Carlo Mazzarella, Alberto Bonucci and Ave Ninchi, directed by Luigi Squarzina, Adolfo Celi, and Mario Landi. Later he met Lucia Ottobrini [it], who became his partner.

After 25 July 1943, with Antonello Trombadori, he formed a group of partisans known as Arditi del Popolo. On 9 September 1943, Fiorentini took part in the battle against the Germans at Porta San Paolo among the ranks of the members of the Action Party; in October he organized and placed himself in command of the central Patriotic Action Groups (GAP), in the IV operational area "Roma centro", taking the battle name of "John"; this formation, together with the GAP Carlo Pisacane, belonged to the partisan structure belonging to the network commanded by Carlo Salinari.

A first GAP action, in which Mario Fiorentini, Rosario Bentivegna (Paolo) and Franco di Lernia (Pietro) took part, was organized to assassinate the Minister of the Interior of Salò Guido Buffarini Guidi and the hierarch Francesco Maria Barracu, intent on dining in a restaurant near Piazza Navona; the action was canceled at the last moment, when the commando was already in place (October 1943). On 31 October, Lucia Ottobrini was added to the three, with cover duties, for an action in Corso Vittorio Emanuele II. The Gappists killed three RSI soldiers, who came out of Palazzo Braschi, after following them almost to Piazza Venezia.

His parents were arrested and taken to the military college of Palazzo Salviati, near the Regina Coeli prison during the Raid of the Ghetto of Rome on 16 October 1943, even though they lived outside the ghetto, in via Capo le Case. The two, along with hundreds of other people, were to have been loaded onto trains to be deported but she bribed a guard with the family jewels, thus managing to escape and take refuge with her sister.

Mario likewise managed to elude capture that day. He had slept at his parents' home the night before and had bombs hidden under his bed, but was not found because the house was not searched; he escaped by fleeing over the roofs.

On 18 November, Fiorentini was responsible for covering some of the Pisacane gappists who entered the Teatro Adriano, having learned that the following day General Stahel, commander of the square in Rome, would be present among high-ranking German officers and republican fascist authorities (including the marshal Rodolfo Graziani). The partisans of the Pisacane placed a fire extinguisher filled with about 3 kg of TNT and equipped with a clockwork device under the stage, but the device failed to explode.