| Mercer Run | |
| Name Other: | Tributary to North Fork Tomlinson Run |
| Map Size: | 300 |
| Pushpin Map: | USA West Virginia#USA |
| Pushpin Map Size: | 300 |
| Pushpin Map Caption: | Location of Mercer Run mouth |
| Pushpin Map Alt: | Map of Mercer Run mouth location |
| Subdivision Type1: | Country |
| Subdivision Name1: | United States |
| Subdivision Type2: | State |
| Subdivision Name2: | West Virginia |
| Subdivision Type3: | County |
| Subdivision Name3: | Hancock |
| Length: | 2.22miles[1] |
| Discharge1 Location: | North Fork Tomlinson Run |
| Discharge1 Avg: | 1.46cuft/s at mouth with North Fork Tomlinson Run[2] |
| Source1: | Cunningham Run divide |
| Source1 Location: | about 4 miles south of Newell, West Virginia |
| Source1 Coordinates: | 40.5867°N -80.5894°W[3] |
| Source1 Elevation: | 1170feet[4] |
| Mouth: | North Fork Tomlinson Run |
| Mouth Location: | about 2.5 miles north of New Manchester, West Virginia |
| Mouth Coordinates: | 40.5583°N -80.5731°W |
| Mouth Elevation: | 974feet[5] |
| Progression: | North Fork Tomlinson Run → Tomlinson Run → Ohio River → Mississippi River → Gulf of Mexico |
| River System: | Ohio River |
| Tributaries Left: | unnamed tributaries |
| Tributaries Right: | unnamed tributaries |
| Bridges: | WV 208, WV 10, Quail Drive |
Mercer Run is a 2.22miles long 1st order tributary to North Fork Tomlinson Run in Hancock County, West Virginia. This is the only stream of this name in the United States.[3]
Mercer Run rises about 4 miles south of Newell, West Virginia, in Hancock County and then flows south to join North Fork Tomlinson Run about 2.5 miles north of New Manchester.[5]
Mercer Run drains of area, receives about 37.9 in/year of precipitation, has a wetness index of 299.58, and is about 63% forested.[2]