| Surname | Name | Country | Age | Gender | Hand |
|---|---|---|---|---|---|
| Jeanjean | Leolia | France | 30 | WTA | Right |
| Jimenez Kasintseva | Victoria | Andorra | 20 | WTA | Left |
| Joint | Maya | Australia | 19 | WTA | Right |
| Jones | Emerson | Australia | 17 | WTA | Right |
| Jones | Francesca | Great Britain | 25 | WTA | Right |
| Jovic | Iva | USA | 18 | WTA | Right |
| Jubb | Paul | Great Britain | 26 | ATP | Right |
| Juncheng | Shang | China | 21 | ATP | Left |
| Juvan | Kaja | Slovenia | 25 | WTA | Right |
| Kalinina | Anhelina | Ukraine | 29 | WTA | Right |
| Kalinskaya | Anna | Russia | 27 | WTA | Right |
| Karatsev | Aslan | Russia | 32 | ATP | Right |
| Kartal | Sonay | Great Britain | 24 | WTA | Right |
| Kasatkina | Darya | Australia | 28 | WTA | Right |
| Kasnikowski | Maks | Poland | 22 | ATP | Right |
| Kecmanovic | Miomir | Serbia | 26 | ATP | Right |
| Kenin | Sofia | USA | 27 | WTA | Right |
| Kerber | Angelique | Germany | 38 | WTA | Left |
| Kessler | McCartney | USA | 26 | WTA | Right |
| Keys | Madison | USA | 31 | WTA | Right |
| Khachanov | Karen | Russia | 29 | ATP | Right |
| Klein | Lukas | Slovakia | 27 | ATP | Right |
| Klugman | Hannah | Great Britain | 17 | WTA | Right |
| Koepfer | Dominik | Germany | 31 | ATP | Left |
| Kokkinakis | Thanasi | Australia | 29 | ATP | Right |
| Kopriva | Vit | Czech Republic | 28 | ATP | Right |
| Korda | Sebastian | USA | 25 | ATP | Right |
| Korneeva | Alina | Russia | 18 | WTA | Right |
| Korpatsch | Tamara | Germany | 30 | WTA | Right |
| Kostovic | Teodora | Serbia | 18 | WTA | Right |
| Kostyuk | Marta | Ukraine | 23 | WTA | Right |
| Kotov | Pavel | Russia | 27 | ATP | Right |
| Kovacevic | Aleksandar | USA | 27 | ATP | Right |
| Kovalik | Jozef | Slovakia | 33 | ATP | Right |
| Kovinic | Danka | Montenegro | 31 | WTA | Right |
| Krejcikova | Barbora | Czech Republic | 30 | WTA | Right |
| Krueger | Ashlyn | USA | 21 | WTA | Right |
| Krueger | Mitchell | USA | 32 | ATP | Right |
| Krunic | Aleksandra | Serbia | 32 | WTA | Right |
| Kubler | Jason | Australia | 32 | ATP | Right |
| Kudermetova | Polina | Uzbekistan | 22 | WTA | Right |
| Kudermetova | Veronika | Russia | 28 | WTA | Right |
| Kudla | Denis | USA | 33 | ATP | Right |
| Kukushkin | Mikhail | Kazakhstan | 38 | ATP | Right |
| Kvitova | Petra | Czech Republic | 35 | WTA | Left |
| Kwon Soon | Woo | South Korea | 28 | ATP | Right |
| Kym | Jerome | Switzerland | 23 | ATP | Right |
| Kypson | Patrick | USA | 26 | ATP | Right |
| Kyrgios | Nick | Australia | 30 | ATP | Right |
| Lajal | Mark | Estonia | 22 | ATP | Right |