Stadium: Court 3 Round: 54 Ground: Clay
| ITF M15 Kamen | 2023/06/26 10:00 | Jack Karlsson Winstrand v Ruben Hartig | 0-6,1-6 |
| Saarlouis, Singles Qualifying M-ITF-GER-07A | 2023/06/18 12:00 | von Der Schulenburg, Jeffrey v Ruben Hartig | 6-1,6-0 |
| ITF M25 Risskov/Aarhus | 2023/06/11 13:25 | Ruben Hartig v Gianluca Cadenasso | 4-6,2-6 |
| ITF - M15 Constanta | 2023/05/29 11:00 | Nicolas Bruna v Ruben Hartig | 7-5,7-6 |
| ITF - M15 Constanta | 2023/05/28 14:00 | Alexandru Luca v Ruben Hartig | 4-6,3-6 |
| ITF - M15 Meerbusch | 2023/04/24 10:00 | Ruben Hartig v Rojas, O. | 6-4,6-4 |
| ITF - M15 Meerbusch | 2023/04/24 08:00 | Leopold Zima v Ruben Hartig | 6-4,6-1 |
| ITF - M15 Antalya | 2023/04/17 12:15 | Marlon Vankan v Ruben Hartig | 6-3,6-3 |
| ITF M15 Kamen | 2023/06/26 10:00 | Lukas Janousek v Luca Hesselmann | 6-4,6-3 |
| ITF M25 Jablonec Nad Nisou | 2023/05/30 09:30 | Matthew William Donald v Lukas Janousek | 6-0,6-2 |
| ITF M25 Jablonec Nad Nisou | 2023/05/29 10:30 | Lukas Janousek v Filip Apltauer | 7-5,2-6,12-10 |
| ITF M25 Most | 2023/05/23 09:50 | Michael Agwi v Lukas Janousek | 6-1,6-3 |
| ITF M25 Most | 2023/05/21 08:00 | Sergo Sikharulidze v Lukas Janousek | 3-6,4-6 |
| ITF - M15 Meerbusch | 2023/04/23 10:30 | Verstegen, Quin v Lukas Janousek | 4-6,6-4,10-8 |
| ITF - M25 Trnava | 2023/03/27 13:00 | Lukas Janousek v Piotr Kusiewicz | 4-6,1-6 |
| ITF - M25 Nussloch | 2023/01/22 08:30 | Noah Thurner v Lukas Janousek | 7-5,6-2 |