| Tatsuya Oishi | |
| Position: | Pitcher / Coach |
| Team: | Saitama Seibu Lions |
| Number: | 95 |
| Birth Date: | 10 October 1988 |
| Bats: | Left |
| Throws: | Right |
| Debutleague: | NPB |
| Debutdate: | April 5 |
| Debutyear: | 2012 |
| Debutteam: | Saitama Seibu Lions |
| Statyear: | 2016 |
| Statleague: | NPB |
| Stat1label: | Win–loss record |
| Stat1value: | 1-6 |
| Stat2label: | ERA |
| Stat2value: | 4.29 |
| Stat3label: | Strikeouts |
| Stat3value: | 72 |
| Teams: | As player
As coach
|
is a Japanese professional baseball pitcher for the Saitama Seibu Lions in Japan's Nippon Professional Baseball.