| Challenger Todi | 07/05 11:00 | 25 | Pedro Cachin vs Lukas Klein | View |
| Wimbledon | 06/28 16:00 | 23 | [132] Liam Broady v Lukas Klein [243] | 4-6,6-3,7-5,6-7,6-3 | |
| Wimbledon | 06/23 10:00 | 19 | [224] Lukas Klein v Andreas Seppi [149] | 6-1,6-7,7-6,7-6 | |
| Wimbledon | 06/22 12:00 | 19 | [114] Yannick Hanfmann v Lukas Klein [224] | 5-7,2-6 | |
| Wimbledon | 06/20 14:50 | 14 | [224] Lukas Klein v Billy Harris [323] | 6-3,6-4 | |
| Challenger Bratislava | 06/07 13:10 | 25 | [225] Lukas Klein v Fabian Marozsan [329] | 4-6,4-6 | |
| Challenger Prostejov | 06/03 09:00 | 28 | [202] Dalibor Svrcina v Lukas Klein [326] | 7-5,6-2 | |
| Challenger Prostejov | 06/02 09:00 | 27 | [313] Benjamin Hassan v Lukas Klein [326] | 6-7,5-7 | |
| Challenger Prostejov | 06/01 11:05 | 26 | [327] Lukas Klein v Enzo Couacaud [184] | 6-2,6-3 | |
| Challenger Prostejov | 05/31 12:45 | 25 | [467] Alexander Erler v Lukas Klein [327] | 4-6,0-6 | |
| Challenger Troisdorf | 05/29 11:00 | 29 | [327] Lukas Klein v Zizou Bergs [200] | 6-2,6-4 | |
| Challenger Troisdorf | 05/28 15:25 | 28 | [342] Henri Squire v Lukas Klein [327] | 4-6,1-6 | |
| Challenger Troisdorf | 05/27 13:45 | 27 | [151] Hugo Grenier v Lukas Klein [327] | 6-7,4-6 |
Lukáš Klein (born 22 March 1998) is a Slovak tennis player. Klein has a career-high ATP singles ranking of World No. 236, achieved on 1 November 2021. He also has a career-high doubles ranking of World No. 240, achieved on 5 April 2021.
Klein has reached 10 career singles finals, with a record of 6 wins and 4 losses all on the ITF Futures Tour. Additionally, he has reached 11 career doubles finals, with a record of 5 wins and 6 losses, including a 1–3 result in ATP Challenger finals. He won the doubles title at the 2021 Challenger La Manche with compatriot Alex Molčan 1–6, 7–5, [10–6].