| Challenger - Todi | 07/04 10:20 | 19 | [333] Pedro B Dias v Giovanni Fonio [441] | 3-6,2-6 | |
| Challenger - Todi | 07/03 11:25 | 14 | Mohamed Safwat v Giovanni Fonio | 0-6,1-6 | |
| Challenger - Troyes | 06/27 15:00 | 19 | [367] Clement Tabur v Giovanni Fonio [441] | 6-7,7-5,7-6 | |
| Challenger - Troyes | 06/26 14:05 | 14 | Boris Fassbender v Giovanni Fonio | 0-6,2-6 | |
| Challenger - Milaan | 06/22 13:20 | 26 | [457] Giovanni Fonio v Alexander Shevchenko [173] | 3-6,6-7 | |
| Challenger - Milaan | 06/21 08:30 | 25 | [457] Giovanni Fonio v Matteo Martineau [375] | 6-3,7-6 | |
| Challenger - Milaan | 06/20 10:45 | 19 | [398] Samuel Vincent Ruggeri v Giovanni Fonio [457] | 5-7,0-6 | |
| Challenger - Milaan | 06/19 12:25 | 14 | Simone Roncalli v Giovanni Fonio | 6-4,2-6,5-7 | |
| Challenger - Perugia | 06/06 08:00 | 19 | [450] Giovanni Fonio v Elliot Benchetrit [447] | 6-7,6-7 | |
| Challenger - Perugia | 06/05 08:00 | 14 | [282] Michael Geerts v Giovanni Fonio [470] | 3-6,6-3,5-7 | |
| Challenger - Forlì | 05/30 08:00 | 19 | [282] Kimmer Coppejans v Giovanni Fonio [471] | 3-6,6-4,7-6 | |
| Challenger - Forlì | 05/29 08:00 | 14 | [471] Giovanni Fonio v Maxime Janvier [285] | 6-7,6-4,6-4 | |
| Challenger - Vicenza | 05/25 15:00 | 26 | [471] Giovanni Fonio v Andrea Pellegrino [222] | 6-7,3-6 | |
| Challenger - Vicenza | 05/24 08:30 | 25 | [471] Giovanni Fonio v Genaro Alberto Olivieri [249] | 6-3,6-4 | |
| Challenger - Vicenza | 05/23 08:00 | 19 | [352] Mats Rosenkranz v Giovanni Fonio [471] | 4-6,3-6 | |
| Challenger - Vicenza | 05/22 08:00 | 14 | Giorgio Tabacco v Giovanni Fonio | 0-6,0-6 | |
| Challenger - Francavilla | 05/16 17:00 | 25 | [307] Hernan Casanova v Giovanni Fonio [457] | 7-6,6-1 | |
| ATP - Rome | 05/07 13:30 | 14 | [460] Giovanni Fonio v Emil Ruusuvuori [59] | 4-6,7-6,3-6 | |
| ITF - M25 Santa Margherita | 04/20 12:00 | 26 | Giovanni Fonio v Gabriele Piraino | 2-6,5-7 | |
| ITF - M25 Santa Margherita | 04/19 14:10 | 25 | Giovanni Fonio v Toby Martin | 6-0,6-2 | |
| ITF - M25 Santa Margherita | 04/12 16:15 | 25 | [489] Matteo Gigante v Giovanni Fonio [454] | 4-6,7-5,7-6 | |
| Challenger - Sanremo | 04/04 08:00 | 19 | [455] Giovanni Fonio v Mate Valkusz [402] | 7-5,4-6,4-6 | |
| Challenger - Sanremo | 04/03 09:30 | 14 | [416] Giovanni Fonio v Alexander Weis [468] | 6-4,6-4 | |
| Challenger - Lugano | 03/27 12:35 | 14 | [299] Ruben Bemelmans v Giovanni Fonio [416] | 7-5,6-4 | |
| ITF M25 - Opatija | 03/22 10:45 | 25 | [489] Francesco Passaro v Giovanni Fonio [414] | 6-0,4-6,6-2 | |
| ITF M25 - Rovinj | 03/15 12:35 | 25 | [362] Ergi Kirkin v Giovanni Fonio [414] | 6-4,7-6 | |
| ITF M25 - Poreč | 03/09 10:45 | 25 | [335] Filip Misolic v Giovanni Fonio [414] | 7-6,6-4 | |
| ITF - M25 Antalya | 02/26 09:15 | 27 | [367] Daniel Michalski v Giovanni Fonio [408] | 6-3,4-6,7-5 | |
| ITF - M25 Antalya | 02/25 12:30 | 26 | Giovanni Fonio v Andrea Picchione | Retired | |
| ITF - M25 Antalya | 02/22 11:00 | 25 | Togan Tokac v Giovanni Fonio | 1-6,1-6 |
Giovanni Fonio (born 7 May 1998) is an Italian tennis player. He took his first steps in tennis at the age of 5, at the Piazzano tennis club in Novara.
Fonio has a career high ATP singles ranking of 274 achieved on 4 Dicember 2023. He also has a career high doubles ranking of 406 achieved on 15 January 2024.
Fonio has won 2 ATP Challenger doubles title: at the 2023 Internazionali di Tennis del Friuli Venezia Giulia with Francesco Forti and at the 2021 Antalya Challenger III with Riccardo Bonadio.
The greatest victory achieved by Giovanni was certainly during the Yokkaichi Challenger in Japan, on 30 November 2023, when he beat the then top 100 player Yosuke Watanuki in 3 sets (3-6 / 6-2 / 7-5).
An important presence in high-level tournaments was certainly in May 2022 at the qualifiers at the Internazionali d’Italia, unfortunately he lost against Emil Ruusuvuori 2-1 (4-6 / 7-6 / 3-6).