Giuseppe Di Vittorio (11 August 1892 – 3 November 1957), also known as Mario Nicoletti, was an Italian trade union leader and communist politician.

As a native of the Mezzogiorno, Di Vittorio became involved in the union plans for solving the region's acute problems in the manner illustrated by the Fasci Siciliani in final decade of the 19th century.

Di Vittorio joined the Republican side fighting Francisco Franco's forces during the Spanish Civil War, he was Political Commissar of the XI International Brigade.

As a union representative, Di Vittorio sat on the National Council, an advisory body created to fulfill the role of a provisional legislature from September 1945 to June 1946.

When a right-wing student attempted to assassinate the PCI leader Palmiro Togliatti in July 1948, CGIL called a general strike and organised street protests during which widespread rioting occurred.

They were followed in May 1949 by supporters of the Italian Democratic Socialist Party, which split from the PSI and left to form what would become the Unione Italiana del Lavoro (UIL).

[5] According to Antonio Giolitti, this position was supported by Di Vittorio himself during private meetings, and archival documents show that the CGIL secretary faced pressure from the PCI leadership to retract the statements.

[6][7] Di Vittorio continued leading CGIL as Italy's largest union with the backing of the PCI and PSI until his death from heart attack in 1957.