| Singles | |
|---|---|
| 2023 Kobe Challenger | |
| Champion |  Duje Ajduković |
| Runner-up |  Sho Shimabukuro |
| Score | 6–4, 6–2 |
Yosuke Watanuki was the defending champion [1] but chose not to defend his title.
Duje Ajduković won the title after defeating Sho Shimabukuro 6–4, 6–2 in the final.
Jurij Rodionov (quarterfinals) Shintaro Mochizuki (quarterfinals)
Luca Nardi (semifinals)
Benjamin Hassan (second round) Sho Shimabukuro (final)
Marc Polmans (quarterfinals)
Bu Yunchaokete (withdrew)
Zdeněk Kolář (first round)| Semifinals | Final | ||||||||||||
| Duje Ajduković | 7 | 5 | 6 | ||||||||||
 Wu Tung-lin | 5 | 7 | 3 | ||||||||||
| Duje Ajduković | 6 | 6 | |||||||||||
| 5 | Sho Shimabukuro | 4 | 2 | ||||||||||
| 3 | Luca Nardi | 2 | 2 | ||||||||||
| 5 | Sho Shimabukuro | 6 | 6 | ||||||||||
| First round | Second round | Quarterfinals | Semifinals | ||||||||||||||||||||||||
| 1 | J Rodionov | 77 | 6 | ||||||||||||||||||||||||
| Q | Y Uchiyama | 65 | 4 | 1 | J Rodionov | 6 | 2 | 6 | |||||||||||||||||||
| WC | T Ito | 66 | 3 | Y Shimizu | 1 | 6 | 1 | ||||||||||||||||||||
| Y Shimizu | 78 | 6 | 1 | J Rodionov | 65 | 6 | 1 | ||||||||||||||||||||
| D Ajduković | 6 | 6 | D Ajduković | 77 | 4 | 6 | |||||||||||||||||||||
 M Efstathiou | 2 | 2 | D Ajduković | 6 | 5 | 6 | |||||||||||||||||||||
| Y-h Hsu | 4 | 3 | LL | R Noguchi | 0 | 7 | 3 | ||||||||||||||||||||
| LL | R Noguchi | 6 | 6 | D Ajduković | 7 | 5 | 6 | ||||||||||||||||||||
| 4 | B Hassan | 0 | 6 | 6 | T-l Wu | 5 | 7 | 3 | |||||||||||||||||||
| J McCabe | 6 | 3 | 2 | 4 | B Hassan | 3 | 4 | ||||||||||||||||||||
| D Sweeny | 3 | 62 | T-l Wu | 6 | 6 | ||||||||||||||||||||||
| T-l Wu | 6 | 77 | T-l Wu | 6 | 6 | ||||||||||||||||||||||
| WC | Renta Tokuda | 6 | 1 | 2 | J Jung | 4 | 3 | ||||||||||||||||||||
| Q |  Y-s Chung | 4 | 6 | 6 | Q | Y-s Chung | 77 | 3 | 1r | ||||||||||||||||||
| J Jung | 6 | 77 | J Jung | 62 | 6 | 4 | |||||||||||||||||||||
| 8 | Z Kolář | 4 | 64 | ||||||||||||||||||||||||
| First round | Second round | Quarterfinals | Semifinals | ||||||||||||||||||||||||
| 6 | M Polmans | 6 | 7 | ||||||||||||||||||||||||
| Q |  Andrew Fenty | 2 | 5 | 6 | M Polmans | 6 | 77 | ||||||||||||||||||||
| A Martin | 4 | 4 |  G Blancaneaux | 4 | 63 | ||||||||||||||||||||||
| G Blancaneaux | 6 | 6 | 6 | M Polmans | 2 | 4 | |||||||||||||||||||||
| Q |  A Holmgren | 6 | 6 | 3 | L Nardi | 6 | 6 | ||||||||||||||||||||
 M Echargui | 4 | 3 | Q | A Holmgren | 3 | 6 | 5 | ||||||||||||||||||||
| WC | T Ichikawa | 5 | 2 | 3 | L Nardi | 6 | 3 | 7 | |||||||||||||||||||
| 3 | L Nardi | 7 | 6 | 3 | L Nardi | 2 | 2 | ||||||||||||||||||||
| 5 | S Shimabukuro | 6 | 77 | 5 | S Shimabukuro | 6 | 6 | ||||||||||||||||||||
| K Uchida | 1 | 65 | 5 | S Shimabukuro | 6 | 77 | |||||||||||||||||||||
| Alt | O Jasika | 3 | 1 | S-c Hong | 4 | 64 | |||||||||||||||||||||
| S-c Hong | 6 | 6 | 5 | S Shimabukuro | 6 | 6 | |||||||||||||||||||||
| Q |  K Ivanovski | 1 | 0r | 2 | S Mochizuki | 3 | 3 | ||||||||||||||||||||
| LL | Y Bai | 6 | 4 | LL | Y Bai | 3 | 2 | ||||||||||||||||||||
| Q | G Fonio | 6 | 2 | 3 | 2 | S Mochizuki | 6 | 6 | |||||||||||||||||||
| 2 | S Mochizuki | 4 | 6 | 6 | |||||||||||||||||||||||
Ilya Ivashka was the defending champion but chose not to defend his title.
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.
Frances Tiafoe was the defending champion, but lost in the first round to Dan Evans.
Peter Polansky was the defending champion but lost in the semifinals to Yasutaka Uchiyama.
Lloyd Harris 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.
Ričardas Berankis was the defending champion but chose not to defend his title.
Taylor Fritz defeated Frances Tiafoe in the final, 7–6(7–3), 7–6(7–2) to win the singles tennis title at the 2022 Japan Open.
Kwon Soon-woo 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.
Dennis Novak was the defending champion but lost in the semifinals to Arthur Cazaux.
Arthur Cazaux was the defending champion but lost in the final to Sho Shimabukuro.
Roberto Carballés Baena was the defending champion but chose not to defend his title.
Andrea Pellegrino was the defending champion but chose not to defend his title.
Dan Evans defeated Tallon Griekspoor in the final, 7–5, 6–3 to win the men's singles tennis title at the 2023 Washington Open. It was his second ATP Tour singles title.
Adrian Mannarino defeated Sebastian Korda in the final, 4–6, 6–3, 6–2 to win the singles tennis title at the 2023 Astana Open. Mannarino won his second ATP Tour title of the season. Korda was contending for his first ATP Tour hardcourt title, but suffered a fifth loss in a tour-level hardcourt final.
Hong Seong-chan was the defending champion but lost in the first round to Luca Nardi.