| Jack Fifield | |
| Position: | Pitcher |
| Birth Date: | October 5, 1871 |
| Birth Place: | Enfield, New Hampshire |
| Death Place: | Syracuse, New York |
| Bats: | Right |
| Throws: | Right |
| Debutleague: | MLB |
| Debutdate: | April 28 |
| Debutyear: | 1897 |
| Debutteam: | Philadelphia Phillies |
| Finalleague: | MLB |
| Finaldate: | October 12 |
| Finalyear: | 1899 |
| Finalteam: | Washington Senators |
| Statleague: | MLB |
| Stat1label: | Win–loss record |
| Stat1value: | 21–39 |
| Stat2label: | Earned run average |
| Stat2value: | 4.59 |
| Stat3label: | Strikeouts |
| Stat3value: | 89 |
| Teams: | |
John Proctor Fifield (October 5, 1871 – November 27, 1939) was a Major League Baseball pitcher.