| Firth River | |
| Subdivision Type1: | Countries |
| Subdivision Name1: | United States, Canada |
| Subdivision Type2: | States |
| Subdivision Name2: | Alaska, Yukon |
| Source1 Coordinates: | 68.4778°N -141.8919°W |
| Mouth: | Beaufort Sea, Arctic Ocean |
| Mouth Location: | South of Herschel Island |
| Mouth Coordinates: | 69.55°N -139.5°W[1] |
| Mouth Elevation: | 0feet |
Firth River is a major river in Yukon, Canada. It begins at the east side of Davidson Mountains and flows into the Beaufort Sea of the Arctic Ocean, just south of Herschel Island.