| Elmer Koestner | |
| Position: | Pitcher |
| Birth Date: | 30 November 1885 |
| Birth Place: | Piper City, Illinois, U.S. |
| Death Place: | Fairbury, Illinois, U.S. |
| Bats: | Right |
| Throws: | Right |
| Debutleague: | MLB |
| Debutdate: | April 23 |
| Debutyear: | 1910 |
| Debutteam: | Cleveland Naps |
| Finalleague: | MLB |
| Finaldate: | July 1 |
| Finalyear: | 1914 |
| Finalteam: | Cincinnati Reds |
| Statleague: | MLB |
| Stat1label: | Pitching Record |
| Stat2label: | Earned run average |
| Stat3label: | Strikeouts |
| Stat1value: | 5-10 |
| Stat2value: | 3.18 |
| Stat3value: | 56 |
| Teams: |
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Elmer Joseph Koestner (November 30, 1885 – October 27, 1959) was a Major League Baseball pitcher who played for two seasons. He played for the Cleveland Naps in 1910 and the Chicago Cubs and Cincinnati Reds in 1914.