| Province: | Ontario |
| Fed-Status: | defunct |
| Fed-Created: | 1924 |
| Fed-Abolished: | 1933 |
| Fed-Election-First: | 1925 |
| Fed-Election-Last: | 1930 |
Port Arthur—Thunder Bay was a federal electoral district represented in the House of Commons of Canada from 1925 to 1935. It was located in the province of Ontario. This riding was created in 1924 from parts of Algoma West and Port Arthur and Kenora ridings.
It consisted of the north-east parts of the territorial districts of Kenora and Thunder Bay.
The electoral district was abolished in 1933 when it was merged into Port Arthur riding.
This riding has elected the following members of Parliament:
|- |Conservative|William Fitzgerald Langworthy|align="right"| 3,277 |Independent Conservative|John James Carrick|align="right"| 2,424 |Liberal|Isaac Lamont Matthews |align="right"| 2,413 |Canadian Labour|Albert Edward Smith |align="right"| 1,363 |}|- |Conservative|Donald James Cowan|align="right"| 4,349 |Liberal–Labour|Alexander Jarvis McComber|align="right"| 2,990 |Canadian Labour|Albert Edward Smith |align="right"| 1,382 |}|- |Conservative|Donald James Cowan|align="right"| 6,371 |Liberal|John James Carrick|align="right"| 4,415 |}