| Port Tobacco River | |
| Mouth Location: | Potomac River |
| Subdivision Type1: | Country |
| Subdivision Name1: | United States |
| Subdivision Type2: | State |
| Subdivision Name2: | Maryland |
| Subdivision Type3: | County |
| Subdivision Name3: | Charles County |
| Length: | 4.2miles |
| Mouth Elevation: | 0feet |
The Port Tobacco River is a tidal tributary of the Potomac River in Charles County, Maryland, in the United States. The river is about long.[1] Port Tobacco, the county seat of Charles County from 1658 to 1895, was an active port until that portion of the river became silted and unnavigable. When the railroad bypassed the town, business declined, and the county seat was moved to La Plata, Maryland.