| ITF - W60 Hechingen | 08/01 16:45 | 25 | Sofia Costoulas v Stephanie Wagner | 6-2,6-3 | |
| ITF - W40 Porto | 07/19 18:35 | 25 | Sofia Costoulas v Daria Khomutsianskaya | 3-6,6-7 | |
| ITF - W25 Corroios-Seixal | 07/12 10:00 | 25 | Aliona Falei v Sofia Costoulas | 6-4,2-6,6-3 | |
| ITF - W25 Tainan | 06/20 03:40 | 25 | [285] Sofia Costoulas v Yi Tsen Cho [414] | 3-6,4-6 | |
| ITF - W25 Tainan | 06/15 04:35 | 26 | [476] Ayano Shimizu v Sofia Costoulas [281] | 6-4,3-6,7-6 | |
| ITF - W25 Tainan | 06/14 04:10 | 25 | Samantha Imbo Nloga v Sofia Costoulas | 2-6,1-6 | |
| ITF - W25 Troisdorf | 05/31 12:20 | 25 | Sofia Costoulas v Gina M Dittmann | 3-6,6-3,5-7 | |
| ITF - W60 Grado | 05/24 11:25 | 26 | [325] Sofia Costoulas v Hailey Baptiste [244] | 3-6,2-6 | |
| ITF - W60 Grado | 05/23 07:30 | 25 | [338] Anna Siskova v Sofia Costoulas [325] | 0-6,1-6 | |
| ITF - W25 Feld Am See | 05/20 10:05 | 29 | Lara Salden v Sofia Costoulas | 3-6,1-6 | |
| ITF - W25 Feld Am See | 05/19 09:00 | 28 | [326] Sofia Costoulas v Elvina Kalieva [243] | 6-2,6-3 | |
| ITF - W25 Feld Am See | 05/18 08:00 | 27 | [345] Maja Chwalinska v Sofia Costoulas [326] | 4-6,4-6 | |
| ITF - W25 Feld Am See | 05/17 11:00 | 26 | [367] Kayla Cross v Sofia Costoulas [326] | 7-5,5-7,3-6 | |
| ITF - W25 Feld Am See | 05/17 07:30 | 25 | Arabella Koller v Sofia Costoulas | 6-4,4-6,1-6 | |
| ITF - W25 Osijek | 04/27 10:40 | 26 | [334] Sofia Costoulas v Tena Lukas [233] | 4-6,1-6 | |
| ITF - W25 Osijek | 04/26 09:30 | 25 | [334] Sofia Costoulas v Julia Avdeeva [465] | 2-6,6-3,7-6 | |
| ITF - W60 Bellinzona | 04/17 12:35 | 24 | [342] Andrea Lazaro Garcia v Sofia Costoulas [358] | 7-5,6-3 | |
| ITF - W25 Santa Margherita | 04/15 11:50 | 28 | [411] Andreea Prisacariu v Sofia Costoulas [360] | 6-1,1-6,6-2 | |
| ITF - W25 Santa Margherita | 04/14 11:10 | 27 | Sofia Costoulas v Federica Bilardo | 6-4,6-4 | |
| ITF - W25 Santa Margherita | 04/13 08:30 | 26 | [301] Matilde Paoletti v Sofia Costoulas [360] | 1-6,3-6 | |
| ITF - W25 Santa Margherita | 04/11 14:15 | 25 | [360] Sofia Costoulas v Ikumi Yamazaki [426] | 7-6,6-2 | |
| ITF - W60 Pretoria | 03/16 08:00 | 26 | [192] Ipek Oz v Sofia Costoulas [347] | 7-6,6-1 | |
| ITF - W60 Pretoria | 03/14 09:25 | 25 | [347] Sofia Costoulas v Lucie Nguyen Tan [378] | 6-3,6-1 | |
| ITF - W25 Pretoria | 03/11 08:00 | 28 | [347] Sofia Costoulas v Emina Bektas [325] | 3-6,6-4,6-7 | |
| ITF - W25 Pretoria | 03/10 08:00 | 27 | [338] Jenny Duerst v Sofia Costoulas [347] | 4-6,3-6 | |
| ITF - W25 Pretoria | 03/09 09:40 | 26 | [366] Alice Tubello v Sofia Costoulas [347] | 2-6,2-6 | |
| ITF - W25 Pretoria | 03/08 09:50 | 25 | [347] Sofia Costoulas v Selena Janicijevic [210] | 7-6,7-5 | |
| ITF - W25 Santo Domingo | 02/24 14:00 | 27 | [417] Stacey Fung v Sofia Costoulas [361] | 2-6,7-6,6-4 | |
| ITF - W25 Santo Domingo | 02/23 16:35 | 26 | [361] Sofia Costoulas v Sada Nahimana [263] | 6-2,6-0 | |
| ITF - W25 Santo Domingo | 02/22 13:30 | 25 | Sofia Costoulas v Eliessa Vanlangendonck | 6-3,0-6,6-3 |
Sofia Costoulas (born 2 April 2005) is a Belgian tennis player.
Costoulas has a Greek–Congolese father and a Belgian mother.
Costoulas has a career-high singles ranking by the Women's Tennis Association (WTA) of 248 and a best doubles ranking of 229.
On the ITF Junior Circuit, she had a career-high combined ranking of No. 2, achieved on 18 April 2022. She lost the girls' singles final of the 2022 Australian Open to Petra Marčinko. She had already reached the Wimbledon junior doubles final in 2021.