| Katsunori Hirai | |
| Position: | Pitcher |
| Team: | Saitama Seibu Lions |
| Number: | 25 |
| Bats: | Right |
| Throws: | Right |
| Birth Date: | 20 December 1991 |
| Birth Place: | Ichinomiya, Aichi, Japan |
| Debutdate: | May 27 |
| Debutyear: | 2017 |
| Debutteam: | Saitama Seibu Lions |
| Statyear: | April 6, 2022 |
| Statleague: | NPB |
| Stat1label: | Win–loss |
| Stat1value: | 20-15 |
| Stat2label: | ERA |
| Stat2value: | 3.61 |
| Stat3label: | Strikeouts |
| Stat3value: | 274 |
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is a professional Japanese professional baseball pitcher for the Saitama Seibu Lions of Nippon Professional Baseball (NPB). Hirai was selected in the 5th round in the 2016 Nippon Professional Baseball draft. In the 2019 NPB season, Hirai appeared in 81 games, breaking the Pacific League Record for most games pitched, previously held by Kazuhisa Inao.[1]