| John Callahan | |
| Position: | Pitcher |
| Birth Date: | October 3, 1874 |
| Birth Place: | Freeport, Illinois |
| Death Place: | Oklahoma City, Oklahoma |
| Debutleague: | MLB |
| Debutdate: | September 3 |
| Debutteam: | St. Louis Browns |
| Finalleague: | MLB |
| Finaldate: | September 4 |
| Finalteam: | St. Louis Browns |
| Statleague: | MLB |
| Stat1label: | Win–loss record |
| Stat1value: | 0-2 |
| Stat2label: | Strikeouts |
| Stat2value: | 2 |
| Stat3label: | Earned run average |
| Stat3value: | 16.20 |
| Teams: |
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John William Callahan (October 3, 1874 – February 15, 1954) was an American Major League Baseball pitcher. He played for the St. Louis Browns during the season.