| James Irwin Hartt | |
| Office1: | Ontario MPP |
| Term Start1: | 1911 |
| Term End1: | 1919 |
| Predecessor1: | James Brockett Tudhope |
| Successor1: | John Benjamin Johnston |
| Constituency1: | Simcoe East |
| Party: | Conservative |
| Birth Date: | 2 March 1866 |
| Birth Place: | Ireland |
| Death Place: | Orillia, Ontario |
| Occupation: | Businessman |
James Irwin Hartt (March 2, 1866 - February 17, 1935) was an Irish-born lumberman and political figure in Ontario. He represented Simcoe East in the Legislative Assembly of Ontario from 1911 to 1919 as a Conservative member.
The son of Isaac B. Hartt and Jane Irwin, he came to Canada in 1884.[1] In 1897, Hartt married Flora Carter. He ran unsuccessfully for a seat in the Ontario assembly in 1908. Hartt served on the municipal council for Orillia.[1] He died at Orillia in 1935.[2]