| John O'Brien | |
| Bats: | Left |
| Throws: | Right |
| Birth Date: | 13 July 1866 |
| Birth Place: | Saint John, New Brunswick |
| Death Place: | Lewiston, Maine |
| Debutleague: | MLB |
| Debutdate: | April 22 |
| Debutyear: | 1891 |
| Debutteam: | Brooklyn Grooms |
| Finalleague: | MLB |
| Finaldate: | October 7 |
| Finalyear: | 1899 |
| Finalteam: | Pittsburgh Pirates |
| Statleague: | MLB |
| Stat1label: | Batting average |
| Stat1value: | .254 |
| Stat2label: | Home runs |
| Stat2value: | 12 |
| Stat3label: | Runs batted in |
| Stat3value: | 229 |
| Teams: |
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John Joseph O'Brien (July 13, 1866 – May 13, 1913) was a Canadian professional baseball player. He played second base in Major League Baseball between 1891 and 1899.