| Men's singles | |
|---|---|
| 2022 Keio Challenger | |
| Champion |  Christopher O'Connell |
| Runner-up |  Yosuke Watanuki |
| Score | 6–1, 6–7(5–7), 6–3 |
Kwon Soon-woo was the defending champion [1] but chose not to defend his title.
Christopher O'Connell won the title after defeating Yosuke Watanuki 6–1, 6–7(5–7), 6–3 in the final.
Christopher O'Connell (champion) John Millman (quarterfinals, withdrew) Kaichi Uchida (quarterfinals)
Damir Džumhur (quarterfinals)
Wu Tung-lin (quarterfinals) Hiroki Moriya (first round) Yosuke Watanuki (final)
Zdeněk Kolář (first round)| Semifinals | Final | ||||||||||||
| 1 | Christopher O'Connell | 6 | 6 | ||||||||||
| Sho Shimabukuro | 3 | 3 | |||||||||||
| 1 | Christopher O'Connell | 6 | 65 | 6 | |||||||||
| 7 | Yosuke Watanuki | 1 | 77 | 3 | |||||||||
| 7 | Yosuke Watanuki | 7 | 77 | ||||||||||
 Nino Serdarušić | 5 | 65 | |||||||||||
| First round | Second round | Quarterfinals | Semifinals | ||||||||||||||||||||||||
| 1 | C O'Connell | 6 | 77 | ||||||||||||||||||||||||
 R Ramanathan | 4 | 63 | 1 | C O'Connell | 6 | 6 | |||||||||||||||||||||
| WC | S Hazawa | 4 | 2 |  E Kırkın | 3 | 4 | |||||||||||||||||||||
| E Kırkın | 6 | 6 | 1 | C O'Connell | 65 | 77 | 6 | ||||||||||||||||||||
| WC | Tomoya Fujiwara | 78 | 1 | 4 | 5 | T-l Wu | 77 | 64 | 4 | ||||||||||||||||||
| LL | Rimpei Kawakami | 66 | 6 | 6 | LL | R Kawakami | 2 | 4 | |||||||||||||||||||
| PR | Y Sugita | 3 | 3 | 5 | T-l Wu | 6 | 6 | ||||||||||||||||||||
| 5 | T-l Wu | 6 | 6 | 1 | C O'Connell | 6 | 6 | ||||||||||||||||||||
| 4 | D Džumhur | 6 | 6 | S Shimabukuro | 3 | 3 | |||||||||||||||||||||
| Q | Ryota Tanuma | 3 | 1 | 4 | D Džumhur | 5 | 6 | 6 | |||||||||||||||||||
| Q | J Trotter | 6 | 6 | Q | J Trotter | 7 | 4 | 4 | |||||||||||||||||||
| Q |  J Mridha | 4 | 1 | 4 | D Džumhur | 4 | 1 | ||||||||||||||||||||
| S Shimabukuro | 6 | 6 | S Shimabukuro | 6 | 6 | ||||||||||||||||||||||
| Q | Yuki Mochizuki | 2 | 4 | S Shimabukuro | 6 | 6 | |||||||||||||||||||||
| J Jung | 6 | 6 | J Jung | 4 | 3 | ||||||||||||||||||||||
| 8 | Z Kolář | 2 | 1 | ||||||||||||||||||||||||
| First round | Second round | Quarterfinals | Semifinals | ||||||||||||||||||||||||
| 7 | Yo Watanuki | 6 | 6 | ||||||||||||||||||||||||
| N Nakagawa | 4 | 4 | 7 | Yo Watanuki | 5 | 6 | 2 | ||||||||||||||||||||
 NH Lý | 6 | 4 | 0 | PR | T Ito | 7 | 0 | 1r | |||||||||||||||||||
| PR | T Ito | 4 | 6 | 6 | 7 | Yo Watanuki | 7 | 4 | 6 | ||||||||||||||||||
| WC | M Imamura | 3 | 4 | 3 | K Uchida | 5 | 6 | 3 | |||||||||||||||||||
 Y-s Chung | 6 | 6 | Y-s Chung | 64 | 3 | ||||||||||||||||||||||
| Q | S-c Hong | 6 | 5 | 3 | 3 | K Uchida | 77 | 6 | |||||||||||||||||||
| 3 | K Uchida | 3 | 7 | 6 | 7 | Yo Watanuki | 7 | 77 | |||||||||||||||||||
| 6 | H Moriya | 67 | 6 | 4 | N Serdarušić | 5 | 65 | ||||||||||||||||||||
 FC Jianu | 79 | 0 | 6 | FC Jianu | 4 | 6 | 5 | ||||||||||||||||||||
| S Mochizuki | 3 | 77 | 1 | N Serdarušić | 6 | 4 | 7 | ||||||||||||||||||||
| N Serdarušić | 6 | 65 | 6 | N Serdarušić | w/o | ||||||||||||||||||||||
| ND Ionel | 5 | 2 | 2 | J Millman | |||||||||||||||||||||||
 F Ferreira Silva | 7 | 6 | F Ferreira Silva | 3 | 2 | ||||||||||||||||||||||
| Q | T Ichikawa | 3 | 65 | 2 | J Millman | 6 | 6 | ||||||||||||||||||||
| 2 | J Millman | 6 | 77 | ||||||||||||||||||||||||
Félix Auger-Aliassime and Denis Shapovalov were the defending champions, however Shapovalov withdrew due to injury. Auger-Aliassime played alongside Benjamin Sigouin, but lost in the final to Juan Carlos Aguilar and Felipe Meligeni Alves, 3–6, 6–7(4–7).
Alexander Zverev was the defending champion and successfully defended his title, defeating Alex de Minaur in the final, 6–2, 6–4.
David Goffin was the defending champion, but withdrew before the competition began.
Matthew Ebden was the defending champion but chose not to defend his title.
Stéphane Robert was the defending champion but chose not to defend his title.
Frances Tiafoe was the defending champion, but lost in the first round to Dan Evans.
Lloyd Harris was the defending champion but chose not to defend his title.
James Duckworth was the defending champion but chose not to defend his title.
Jordan Thompson was the defending champion but chose not to defend his title.
Rogério Dutra Silva was the defending champion but chose not to defend his title.
This was the first edition of the tournament.
Maxime Cressy was the defending champion but lost in the third round to Ulises Blanch.
Ričardas Berankis was the defending champion but chose not to defend his title.
Yosuke Watanuki was the defending champion and successfully defended his title, defeating Frederico Ferreira Silva 6–7(3–7), 7–5, 6–4 in the final.
Yūichi Sugita was the defending champion but lost in the second round to Colin Sinclair.
Kwon Soon-woo defeated Roberto Bautista Agut in the final, 6–4, 3–6, 7–6(7–4) to win the men's singles tennis title at the 2023 Adelaide International 2. It was his second ATP Tour singles title, and he became just the tenth man in ATP Tour history to win a title as a lucky loser.
Fernando Verdasco was the defending champion but chose not to defend his title.
Daniil Medvedev defeated Jannik Sinner in the final, 7–5, 6–3 to win the men's singles tennis title at the 2023 Miami Open. It was his fifth ATP Tour Masters 1000 title, fourth title of 2023, and 19th career title overall. He became only the eighth man to win 5 or more ATP Masters Titles.
Frances Tiafoe defeated Jan-Lennard Struff in the final, 4–6, 7–6(7–1), 7–6(10–8) to win the singles title at the 2023 Stuttgart Open. It was his third ATP Tour title, and his first on grass courts. Tiafoe saved a championship point en route to the title, in the final-set tiebreak. By winning the title, Tiafoe debuted in the top ten of the ATP rankings for the first time in his career.
Yasutaka Uchiyama was the defending champion but retired from his second round match against Christopher O'Connell.