Giovanni Bacci (7 March 1857 – 9 August 1928) was an Italian journalist and politician.

In 1903, he became a member of the PSI, and in 1912 he was appointed director of the party's newspaper Avanti!

In 1921, Bacci was elected as secretary of the PSI, which suffered a split that led to the foundation of the Communist Party of Italy.

Under his leadership, the PSI was confirmed as the first party in the country with 24.7% of votes but lost 33 seats.

After the formation of the Italian fascist dictatorship of Benito Mussolini, Bacci was banned from politics and died few years later in 1928 in Milan.