| William James Duffy | |
| Office: | Member of the Legislative Assembly of Quebec for Compton |
| Predecessor: | Andrew Ross McMaster |
| Successor: | Payson Sherman |
| Term Start: | 1931 |
| Term End: | 1935 |
| Predecessor2: | Payson Sherman |
| Successor2: | Charles Daniel French |
| Term Start2: | 1939 |
| Term End2: | 1946 |
| Birth Date: | 21 November 1888 |
| Birth Place: | South Durham, Quebec |
| Death Place: | Gould, Quebec |
| Party: | Liberal |
William James Duffy (November 21, 1888 - January 18, 1946) was a Canadian provincial politician.
Born in South Durham, Quebec, Duffy was the member of the Legislative Assembly of Quebec for Compton from 1931 to 1935 and 1939 to 1946.