| Hirotaka Koishi | |
| Position: | Pitcher |
| Bats: | Left |
| Throws: | Left |
| Birth Date: | 13 April 1987 |
| Birth Place: | Hayami District, Ōita, Japan |
| Debutdate: | April 26 |
| Debutyear: | 2012 |
| Debutteam: | Saitama Seibu Lions |
| Statyear: | 2016 season |
| Statleague: | NPB |
| Stat1label: | Win–loss record |
| Stat1value: | 1–5 |
| Stat2label: | Saves |
| Stat2value: | 1 |
| Stat3label: | ERA |
| Stat3value: | 4.61 |
| Stat4label: | Strikeouts |
| Stat4value: | 87 |
| Teams: | |
is a professional Japanese baseball player. He plays pitcher for the Saitama Seibu Lions.