| 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 - Lisboa | 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 - Génova | 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 - Augsburgo | 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).