| Keio Challenger | |
| Type: | joint |
| Current: | 2023 Keio Challenger |
| Event Name: | Keio Challenger |
| Location: | Yokohama, Japan |
| Venue: | Mamushidani Tennis Courts, Keio University |
| Surface: | Hard |
| Website: | Website |
| Atp Category: | ATP Challenger Tour |
| Atp Draw: | 32S/32Q/16D |
| Atp Prize Money: | $50,000+H |
| Wta Tier: | ITF Women's Circuit |
| Wta Draw: | 32S/32Q/16D |
| Wta Prize Money: | $25,000 |
The Keio Challenger is a professional tennis tournament played on hardcourts. It is currently part of the ATP Challenger Tour and the ITF Women's Circuit. Having been held in Yokohama, Japan since 1999, the women's edition of the event was introduced in 2017.
| Year | Champion | Runner-up | Score | |
|---|---|---|---|---|
 Yosuke Watanuki | 7–6(7–5), 6–4 | |||
 Christopher O'Connell | 6–1, 6–7(5–7), 6–3 | |||
| 2020–21 | Not held | |||
 Kwon Soon-woo | 7–6(7–4), 6–3 | |||
| Yasutaka Uchiyama | 2–6, 6–3, 6–4 | |||
| Yūichi Sugita | 6–4, 2–6, 7–6(7–2) | |||
| 2016 | Not held | |||
| Taro Daniel | 4–6, 6–3, 6–3 | |||
| John Millman | 6–4, 6–4 | |||
| Matthew Ebden | 2–6, 7–6(7–3), 6–3 | |||
 Matteo Viola | 7–6(7–3), 6–3 | |||
| 2010–11 | Not held | |||
| Takao Suzuki | 6–4, 7–6(7−5) | |||
| 2008 | Lee Hyung-taik | 7–5, 6–3 | ||
| 2007 |  Dudi Sela | 6–7(5−7), 6–4, 6–2 | ||
| 2003–06 | Not held | |||
| 2002 | Lee Hyung-taik | 2–6, 7–6(7−2), 7–6(8−6) | ||
| 2001 | Takao Suzuki | 6–2, 6–7(5−7), 7–6(7−4) | ||
| 2000 | Eric Taino | 7–6(7−5), 6–4 | ||
| 1999 | Lee Hyung-taik | 6–3, 6–0 |
| Year | Champions | Runners-up | Score | |
|---|---|---|---|---|
 Filip BergeviMick Veldheer | 2–6, 7–5, [11–9] | |||
 Victor Vlad CorneaRuben Gonzales | 7–5, 6–3 | |||
| 2020–21 | Not held | |||
 Moez Echargui Skander Mansouri | 7–6(8–6), 6–7(3–7), [10–7] | |||
| Tobias Kamke Tim Pütz | 3–6, 7–5, [12–10] | |||
| Marin Draganja Tomislav Draganja | 4–6, 6–3, [10–4] | |||
| 2016 | Not held | |||
 Sanchai Ratiwatana Sonchat Ratiwatana | 6–4, 6–4 | |||
 Bradley Klahn Matt Reid | 4–6, 6–4, [10–7] | |||
Bradley Klahn Michael Venus | 7–5, 6–1 | |||
 Prakash Amritraj Philipp Oswald | 6–3, 6–4 | |||
| 2010–11 | Not Held | |||
| Yang Tsung-hua Yi Chu-huan | 6–7(9−11), 6–3, [12–10] | |||
| 2008 |  Tomáš Cakl Marek Semjan | 6–3, 7–6(7−1) | ||
| 2007 | Hiroki Kondo Go Soeda | 6–7(5−7), 6–3, [11–9] | ||
| 2003–06 | Not held | |||
| 2002 | Lu Yen-hsun Danai Udomchoke | 7–6(7−5), 6–3 | ||
| 2001 | Takao Suzuki Mitsuru Takada | 6–3, 6–4 | ||
| 2000 | Yves Allegro Julian Knowle | 6–3, 7–6(7−2) | ||
| 1999 | Satoshi Iwabuchi Thomas Shimada | 6–2, 6–4 |
| Year | Champion | Runner-up | Score | |
|---|---|---|---|---|
| Han Na-lae | 7–5, 6–0 | |||
| 2021 | Not held | |||
| 2020 | Yuriko Miyazaki | 7–5, 5–7, 6–2 | ||
 Greet Minnen | 6–4, 6–1 | |||
 Veronika Kudermetova | 6–2, 6–4 | |||
| Akiko Omae | 7–5, 6–2 |
| Year | Champions | Runners-up | Score | |
|---|---|---|---|---|
| Saki Imamura Naho Sato | 6–4, 4–6, [10–5] | |||
| 2021 | Not held | |||
| 2020 | Robu Kajitani Naho Sato | 1–6, 6–4, [10–8] | ||
| Choi Ji-hee Han Na-lae | 6–1, 7–5 | |||
 Laura Robson Fanny Stollár | 5–7, 6–2, [10–4] | |||
| Ayaka Okuno Erika Sema | 6–4, 6–4 |