| Challenger Yokohama | 11/19 05:10 | 14 | [306] Giovanni Fonio v Hiroki Moriya [435] | 5-7,6-3,6-4 | |
| Challenger Kobe | 11/14 05:00 | 25 | [306] Giovanni Fonio v Shintaro Mochizuki [137] | 6-4,2-6,3-6 | |
| Challenger Kobe | 11/13 02:55 | 19 | [306] Giovanni Fonio v Shinji Hazawa [315] | 6-3,6-7,6-1 | |
| Challenger Kobe | 11/12 05:25 | 14 | [306] Giovanni Fonio v Hiroki Moriya [428] | 7-5,6-2 | |
| Challenger Matsuyama | 11/07 03:45 | 25 | [155] Sho Shimabukuro v Giovanni Fonio [306] | 5-7,6-4,6-4 | |
| ITF M25 Santa Margherita | 10/25 08:00 | 26 | [306] Giovanni Fonio v Giovanni Oradini [396] | 6-3,3-6,2-6 | |
| ITF M25 Santa Margherita | 10/24 09:00 | 25 | Giovanni Fonio v Giammarco Gandolfi | 6-2,6-3 | |
| ITF M25 Santa Margherita | 10/19 09:20 | 27 | [304] Giovanni Fonio v Nerman Fatic [224] | 6-7,4-6 | |
| ITF M25 Santa Margherita | 10/18 07:55 | 26 | Giovanni Fonio v Luciano Carraro | 6-4,6-2 | |
| ITF M25 Santa Margherita | 10/17 13:25 | 25 | Giovanni Fonio v Andrea Gola | 7-6,6-2 | |
| ITF M25 Santa Margherita | 10/12 08:00 | 27 | [459] Marcello Serafini v Giovanni Fonio [311] | 7-6,6-3 | |
| ITF M25 Santa Margherita | 10/11 09:20 | 26 | Niccolo Catini v Giovanni Fonio | 2-6,3-6 | |
| ITF M25 Santa Margherita | 10/10 09:45 | 25 | Gabriele Piraino v Giovanni Fonio | 6-7,0-6 | |
| Challenger Lisbon | 10/01 10:45 | 14 | [314] Giovanni Fonio v Luka Mikrut [411] | 6-7,3-6 | |
| Challenger Braga | 09/25 11:40 | 19 | [270] Oriol Roca Batalla v Giovanni Fonio [305] | 6-3,6-7,6-1 | |
| Challenger Braga | 09/24 14:10 | 14 | Pedro Araujo v Giovanni Fonio | 1-6,7-5,5-7 | |
| Challenger Sibiu | 09/21 08:40 | 26 | [207] Duje Ajdukovic v Giovanni Fonio [305] | 4-6,6-3,6-2 | |
| Challenger Sibiu | 09/20 10:20 | 25 | [305] Giovanni Fonio v Cezar Cretu [355] | 7-6,6-3 | |
| Challenger Genoa | 09/04 11:50 | 25 | [289] Giovanni Fonio v Franco Agamenone [193] | 6-7,6-4,3-6 | |
| Challenger Como | 08/29 10:35 | 19 | [289] Giovanni Fonio v Valentin Royer [335] | 4-6,4-6 | |
| Challenger Como | 08/28 13:40 | 14 | [289] Giovanni Fonio v David Jorda Sanchis [373] | 4-6,6-3,7-5 | |
| Challenger Augsburg | 08/22 08:00 | 25 | [294] Oliver Crawford v Giovanni Fonio [288] | 6-2,6-3 | |
| Challenger Todi | 08/18 19:00 | 28 | [334] Clement Tabur v Giovanni Fonio [322] | 7-5,4-6,6-3 | |
| Challenger Todi | 08/17 20:10 | 27 | Felix Gill v Giovanni Fonio | 3-6,4-6 | |
| Challenger Todi | 08/16 19:45 | 26 | [322] Giovanni Fonio v Julian Ocleppo [448] | 6-3,6-7,6-4 | |
| Challenger Todi | 08/15 09:55 | 25 | [322] Giovanni Fonio v Orlando Luz [461] | 7-6,6-4 | |
| Challenger Cordenons | 08/08 08:00 | 25 | [323] Giovanni Fonio v Nicholas D Ionel [208] | 3-6,7-5,5-7 | |
| Challenger Liberec | 07/31 14:00 | 25 | [316] Giovanni Fonio v Norbert Gombos [217] | 6-7,4-6 | |
| Challenger Zug | 07/23 09:00 | 14 | Giovanni Fonio v Dylan Dietrich | 3-6,3-6 | |
| Challenger Tampere | 07/17 15:30 | 25 | [289] Giovanni Fonio v Vit Kopriva [249] | 4-6,6-7 |
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).