The 2023 Keio Challenger was a professional tennis tournament played on hard courts. It was the 16th (men's) and 6th (women's) editions of the tournament and part of the 2023 ATP Challenger Tour and the 2023 ITF Women's World Tennis Tour. It took place in Yokohama, Japan between 20 November and 3 December 2023.
| 2023 Keio Challenger | |
|---|---|
| Date | 20 – 26 November (men's) 27 November – 3 December (women's) |
| Edition | 16th (men's) 6th (women's) |
| Category | ATP Challenger Tour ITF Women's World Tennis Tour |
| Surface | Hard |
| Location | Yokohama, Japan |
| Champions | |
| Men's singles | |
 Yosuke Watanuki | |
| Women's singles | |
 Aliona Falei | |
| Men's doubles | |
 Filip Bergevi /  Mick Veldheer | |
| Women's doubles | |
 Liang En-shuo /  Tang Qianhui | |
Men's singles main-draw entrants
Seeds
| Country | Player | Rank1 | Seed |
|---|---|---|---|
| JPN | Yosuke Watanuki | 81 | 1 |
 AUT | Jurij Rodionov | 107 | 2 |
 USA | Michael Mmoh | 109 | 3 |
 AUS | James Duckworth | 113 | 4 |
| USA | |||
 ITA | Luca Nardi | 128 | 6 |
| AUS | Marc Polmans | 158 | 7 |
 SUI | Leandro Riedi | 160 | 8 |
- 1 Rankings are as of 13 November 2023.[1]
Other entrants
The following players received wildcards into the singles main draw:
The following player received entry into the singles main draw as an alternate:
The following players received entry from the qualifying draw:
The following players received entry as lucky losers:
Chung Yun-seong
Mathys Erhard
Giovanni Fonio
Champions
Men's singles
Yosuke Watanuki def. Yuta Shimizu 7–6(7–5), 6–4.
Women's singles
Aliona Falei def. Ayano Shimizu, 6–3, 7–5
Men's doubles
Filip Bergevi / 
Mick Veldheer def. 
Ray Ho / 
Calum Puttergill 2–6, 7–5, [11–9].
Women's doubles
- Liang En-shuo /
Tang Qianhui def. Aoi Ito / Natsumi Kawaguchi, Walkover