Giovanni Fonio (born 7 May 1998) is an Italian tennis player.
Fonio has a career high ATP singles ranking of world No. 269 achieved on 29 January 2024. He also has a career high doubles ranking of No. 406 achieved on 15 January 2024.
Fonio has won 2 ATP Challenger doubles title: at the 2021 Antalya Challenger III with Riccardo Bonadio and at the 2023 Internazionali di Tennis del Friuli Venezia Giulia with Francesco Forti.
In May 2022, at the qualifiers at the Internazionali d’Italia he lost to Emil Ruusuvuori.
On 30 November 2023, at the Yokkaichi Challenger in Japan, he defeated the then top 100 player Yosuke Watanuki in 3 sets.