| Date: | 25 February – 3 March (men's) 4 – 10 March (women's) |
| Edition: | 14th (men's) 3rd (women's) |
| Category: | ATP Challenger Tour ITF Women's World Tennis Tour |
| Surface: | Hard |
| Location: | Yokohama, Japan |
| Champms: |  Kwon Soon-woo |
| Champmd: |  Moez Echargui / Skander Mansouri |
| Champwd: | Choi Ji-hee / Han Na-lae |
| After Year: | 2022 |
The 2019 Keio Challenger was a professional tennis tournament played on hardcourts. It was the 14th (men's) and third (women's) editions of the tournament and part of the 2019 ATP Challenger Tour and the 2019 ITF Women's World Tennis Tour. It took place in Yokohama, Japan between 25 February and 10 March 2019.
| Country | Player | Rank1 | Seed | |
|---|---|---|---|---|
 Japan | Tatsuma Ito | 132 | 1 | |
| Oscar Otte | 156 | 2 | ||
| Japan | Yūichi Sugita | 160 | 3 | |
| Japan | Hiroki Moriya | 177 | 4 | |
| Mats Moraing | 184 | 5 | ||
 Austria | Jurij Rodionov | 191 | 6 | |
| Japan | Go Soeda | 194 | 7 | |
 Israel | Dudi Sela | 195 | 8 | |
| Blaž Rola | 201 | 9 | ||
 Italy | Gianluca Mager | 213 | 10 | |
| Korea, Republic of | Kwon Soon-woo | 225 | 11 | |
 Argentina | Pedro Cachin | 235 | 12 | |
 Brazil | Guilherme Clezar | 237 | 13 | |
 Canada | Filip Peliwo | 238 | 14 | |
 Serbia | Viktor Troicki | 243 | 15 | |
 France | Enzo Couacaud | 249 | 16 |
The following players received wildcards into the singles main draw:
Shinji Hazawa Masamichi Imamura Naoto Kai Sung Yo-han Kaito UesugiThe following player received entry into the singles main draw using a protected ranking:
The following players received entry into the singles main draw using their ITF World Tennis ranking:
The following players received entry from the qualifying draw:
Kim Cheong-euiThe following player received entry as a lucky loser:
Shintaro Imai| Country | Player | Rank1 | Seed | |
|---|---|---|---|---|
| Serbia | Ivana Jorović | 108 | 1 | |
 China | Liu Fangzhou | 173 | 2 | |
 Slovakia | Rebecca Šramková | 182 | 3 | |
| Ylena In-Albon | 183 | 4 | ||
| China | Lu Jiajing | 186 | 5 | |
| Serbia | Dejana Radanović | 195 | 6 | |
| Korea, Republic of | Han Na-lae | 199 | 7 | |
| Japan | Ayano Shimizu | 206 | 8 |
The following players received wildcards into the singles main draw:
Ayumi Hirata Anri Nagata Risa Ozaki Satoko SuenoThe following players received entry into the singles main draw using their ITF World Tennis ranking:
Nudnida Luangnam
Anna Morgina Naho Sato Anna UrekeThe following players received entry from the qualifying draw:
Mayuka Aikawa Shiho Akita
Catherine Harrison Kyōka Okamura Akiko Omae Risa UshijimaSee main article: article and 2019 Keio Challenger – Men's singles.
Kwon Soon-woo def. Oscar Otte 7–6(7–4), 6–3.
Greet Minnen def. 
Elena-Gabriela Ruse, 6–4, 6–1See main article: article and 2019 Keio Challenger – Men's doubles.
Moez Echargui / Skander Mansouri def. 
Max Purcell / Luke Saville 7–6(8–6), 6–7(3–7), [10–7]. Choi Ji-hee / Han Na-lae def. 
Rutuja Bhosale / Akiko Omae, 6–1, 7–5