| John Gallagher | |
| Office1: | Ontario MPP |
| Term Start1: | 1898 |
| Term End1: | 1911 |
| Predecessor1: | Joseph Longford Haycock |
| Successor1: | Anthony McGuin Rankin |
| Constituency1: | Frontenac |
| Party: | Progressive Conservative |
| Birth Date: | 24 April 1849 |
| Birth Place: | Bastard Township, Canada West |
| Death Place: | Portland, Ontario |
| Occupation: | Merchant |
| Spouse: | Miss Mills (m. 1881) |
John S. Gallagher (April 24, 1849 - June 17, 1920) was an Ontario merchant and political figure. He represented Frontenac in the Legislative Assembly of Ontario from 1898 to 1911 as a Conservative member.
He was born in Bastard Township, Leeds County, Upper Canada in 1849.[1] He served as treasurer for the township and was chairman of the High School Board for Leeds. Gallagher was a hay and grain dealer in Harrowsmith. In 1881, he married a Miss Mills. He was an unsuccessful candidate for the provincial assembly in 1894.
He died in Portland on June 17, 1920.[2]