| John O'Brien | |
| Position: | Outfielder |
| Birth Date: | October 22, 1851 |
| Birth Place: | Columbus, Ohio |
| Death Place: | Fall River, Massachusetts |
| Bats: | Unknown |
| Throws: | Right |
| Debutleague: | MLB |
| Debutdate: | April 19 |
| Debutyear: | 1884 |
| Debutteam: | Baltimore Monumentals |
| Finalleague: | MLB |
| Finaldate: | May 31 |
| Finalyear: | 1884 |
| Finalteam: | Baltimore Monumentals |
| Statleague: | MLB |
| Stat1label: | Batting average |
| Stat1value: | .247 |
| Stat2label: | On-base percentage |
| Stat2value: | .266 |
| Stat3label: | Slugging percentage |
| Stat3value: | .286 |
| Teams: |
|
John E. O'Brien (October 22, 1851 – December 31, 1914) was a professional baseball player who played outfielder in the Major Leagues in 1884 for the Baltimore Monumentals of the Union Association. He later played for the Bridgeport Giants of the Eastern League in 1885.