Japan at the 2017 World Aquatics Championships
Japan competed at the 2017 World Aquatics Championships in Budapest, Hungary from 14 July to 30 July.
Diving
Japan has entered 5 divers.;Men
;Women
;Mixed
Open water swimming
Japan has entered six open water swimmers| Athlete | Event | Time | Rank |
| Yasunari Hirai | Men's 5 km | 55:33.3 | 33 |
| Yasunari Hirai | Men's 10 km | 1:54:52.9 | 40 |
| Yohsuke Miyamoto | Men's 5 km | 55:38.0 | 34 |
| Yohsuke Miyamoto | Men's 25 km | 5:11:32.1 | 15 |
| Taiki Nonaka | Men's 10 km | 1:55:14.1 | 44 |
| Taiki Nonaka | Men's 25 km | 5:13:35.5 | 19 |
| Yumi Kida | Women's 10 km | 2:03:06.6 | 23 |
| Yumi Kida | Women's 25 km | 5:39:31.5 | 15 |
| Yukimi Moriyama | Women's 5 km | 1:01:14.5 | 21 |
| Yukimi Moriyama | Women's 10 km | 2:02:13.3 | 20 |
| Minami Niikura | Women's 5 km | 1:00:55.0 | 16 |
| Yukimi Moriyama Minami Niikura Yasunari Hirai Yohsuke Miyamoto | Mixed team | 55:54.0 | 9 |
Swimming
Japanese swimmers have achieved qualifying standards in the following events :;Men
;Women
;Mixed
Synchronized swimming
Japan's synchronized swimming team consisted of 14 athletes.;Women
;Mixed
Legend: = Reserve Athlete
Water polo
Japan qualified both a men's and women's teams.Men's tournament
;Team roster- Katsuyuki Tanamura
- Seiya Adachi
- Shuma Kawamoto
- Mitsuaki Shiga
- Takuma Yoshida
- Atsuto Iida
- Yusuke Shimizu
- Mitsuru Takata
- Atsushi Arai
- Kohei Inaba
- Keigo Okawa
- Kenya Araki
- Tomoyoshi Fukushima
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;Playoffs
;9th–12th place semifinals
;Ninth place game
Women's tournament
;Team roster- Miyuu Aoki
- Yumi Arima
- Yuri Kazama
- Shino Magariyama
- Chiaki Sakanoue
- Minori Yamamoto
- Akari Inaba
- Yuki Niizawa
- Kana Hosoya
- Misaki Noro
- Marina Tokumoto
- Kotori Suzuki
- Minami Shioya
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;13th–16th place semifinals
;13th place game