Japan at the 2019 World Aquatics Championships
Japan competed at the 2019 World Aquatics Championships in Gwangju, South Korea from 12 to 28 July.
Artistic swimming
Japan entered 13 artistic swimmers.;Women
;Mixed
Legend: = Reserve Athlete
Diving
Japan entered seven divers.;Men
;Women
Open water swimming
Japan qualified two male and two female open water swimmers.;Men
| Athlete | Event | Time | Rank |
| Taiki Nonaka | Men's 10 km | 1:51:35.3 | 45 |
| Takeshi Toyoda | Men's 10 km | 1:50:22.0 | 39 |
;Women
| Athlete | Event | Time | Rank |
| Yumi Kida | Women's 10 km | 1:55:26.7 | 22 |
| Minami Niikura | Women's 10 km | 1:55:46.8 | 30 |
;Mixed
Swimming
Japan entered 25 swimmers.;Men
;Women
;Mixed
Legend: = Swimmers who participated in the heat only.
Water polo
Men's tournament
;Team roster- Katsuyuki Tanamura
- Seiya Adachi
- Harukiirario Koppu
- Mitsuaki Shiga
- Takuma Yoshida
- Atsuto Iida
- Yusuke Shimizu
- Mitsuru Takata
- Atsushi Arai
- Yusuke Inaba
- Keigo Okawa
- Kenta Araki
- Tomoyoshi Fukushima
- Coach: Yoji Omoto
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;Playoffs
;9th–12th place semifinals
;Eleventh place game
Women's tournament
;Team roster- Rikako Miura
- Yumi Arima
- Akari Inaba
- Shino Magariyama
- Chiaki Sakanoue
- Miku Koide
- Maiko Hashida
- Yuki Niizawa
- Minori Yamamoto
- Misaki Noro
- Marina Tokumoto
- Kotori Suzuki
- Minami Shioya
- Coach: Makihiro Motomiya
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;13th–16th place semifinals
;13th place game