| 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 Milan | 06/22 13:20 | 26 | [457] Giovanni Fonio v Alexander Shevchenko [173] | 3-6,6-7 | |
| Challenger Milan | 06/21 08:30 | 25 | [457] Giovanni Fonio v Matteo Martineau [375] | 6-3,7-6 | |
| Challenger Milan | 06/20 10:45 | 19 | [398] Samuel Vincent Ruggeri v Giovanni Fonio [457] | 5-7,0-6 | |
| Challenger Milan | 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 Forli | 05/30 08:00 | 19 | [282] Kimmer Coppejans v Giovanni Fonio [471] | 3-6,6-4,7-6 | |
| Challenger Forli | 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 Rzym | 05/07 13:30 | 14 | [460] Giovanni Fonio v Emil Ruusuvuori [59] | 4-6,7-6,3-6 | |
| ITF - Santa Margherita M25 | 04/20 12:00 | 26 | Giovanni Fonio v Gabriele Piraino | 2-6,5-7 | |
| ITF - Santa Margherita M25 | 04/19 14:10 | 25 | Giovanni Fonio v Toby Martin | 6-0,6-2 | |
| ITF - Santa Margherita M25 | 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 - Opatija M25 | 03/22 10:45 | 25 | [489] Francesco Passaro v Giovanni Fonio [414] | 6-0,4-6,6-2 | |
| ITF - Rovinj M25 | 03/15 12:35 | 25 | [362] Ergi Kirkin v Giovanni Fonio [414] | 6-4,7-6 | |
| ITF - Porec M25 | 03/09 10:45 | 25 | [335] Filip Misolic v Giovanni Fonio [414] | 7-6,6-4 | |
| ITF - Antalya M25 | 02/26 09:15 | 27 | [367] Daniel Michalski v Giovanni Fonio [408] | 6-3,4-6,7-5 | |
| ITF - Antalya M25 | 02/25 12:30 | 26 | Giovanni Fonio v Andrea Picchione | Retired | |
| ITF - Antalya M25 | 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).