The 2018 Japan Women's Open was a women's tennis tournament played on outdoor hard courts. It was the tenth edition of the Japan Women's Open, and part of the WTA International tournaments of the 2018 WTA Tour. It was held at the Regional Park Tennis Stadium in Hiroshima, Japan, from September 10 through September 16, 2018. This is the first year that the tournament was held in Hiroshima.[1]
| Event | W | F | SF | QF | Round of 16 | Round of 32 | width=85 | Q | width=85 | Q3 | width=85 | Q2 | width=85 | Q1 |
| Singles | 280 | 180 | 110 | 60 | 30 | 1 | 18 | 14 | 10 | 1 | ||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Doubles | 1 |
| width=130 bgcolor=dfe2e9 | Event | width=80 bgcolor=lime | W | width=85 bgcolor=thistle | F | width=85 bgcolor=ffff00 | SF | width=85 bgcolor=ffebcd | QF | width=85 bgcolor=afeeee | Round of 16 | width=85 bgcolor=afeeee | Round of 321 | width=85 | Q3 | width=85 | Q2 | width=85 | Q1 |
| Singles | $43,000 | $21,400 | $11,300 | $5,900 | $3,310 | $1,925 | $1,005 | $730 | $530 | ||||||||||
| Doubles2 | $12,300 | $6,400 | $3,435 | $1,820 | $960 |
| Country | Player | Rank1 | Seed | |
|---|---|---|---|---|
 China | Zhang Shuai | 34 | 1 | |
| Hsieh Su-wei | 43 | 2 | ||
 Kazakhstan | Yulia Putintseva | 50 | 3 | |
| China | Wang Qiang | 52 | 4 | |
 Australia | Ajla Tomljanović | 58 | 5 | |
| Kazakhstan | Zarina Diyas | 60 | 6 | |
| China | Zheng Saisai | 63 | 7 | |
 Poland | Magda Linette | 68 | 8 |
The following players received wildcards into the singles main draw:
The following player entered the singles main draw with a protected ranking:
The following players received entry from the qualifying draw:
Ana Bogdan → replaced by 
Fiona Ferro
Jennifer Brady → replaced by Jana Fett
Aliaksandra Sasnovich → replaced by Duan Yingying Magdalena Fręch Yulia Putintseva (lower back injury)| Country | Player | Country | Player | Rank1 | Seed |
|---|---|---|---|---|---|
 Japan | Japan | Makoto Ninomiya | 80 | 1 | |
| Japan | China | Zhang Shuai | 94 | 2 | |
| Japan | Shuko Aoyama | China | Duan Yingying | 121 | 3 |
| Viktorija Golubic |  Sweden | Johanna Larsson | 123 | 4 | |
The following pairs received wildcards into the doubles main draw:
Priscilla Hon (gastrointestinal illness)See main article: 2018 Japan Women's Open – Singles.
Amanda Anisimova 6–2, 6–2See main article: 2018 Japan Women's Open – Doubles.
Eri Hozumi / Zhang Shuai def. Miyu Kato / Makoto Ninomiya 6–2, 6–4