| Official Name: | Mill Run, Pennsylvania |
| Settlement Type: | Census-designated place |
| Pushpin Map: | Pennsylvania#USA |
| Pushpin Label: | Mill Run |
| Pushpin Label Position: | top |
| Coordinates: | 40.5056°N -78.4319°W |
| Subdivision Type: | Country |
| Subdivision Name: | United States |
| Subdivision Type1: | State |
| Subdivision Name1: | Pennsylvania |
| Subdivision Type2: | County |
| Subdivision Name2: | Blair |
| Subdivision Type3: | Township |
| Subdivision Name3: | Logan |
| Unit Pref: | Imperial |
| Area Footnotes: | [1] |
| Area Total Sq Mi: | 0.30 |
| Area Land Sq Mi: | 0.30 |
| Area Water Sq Mi: | 0.00 |
| Area Total Km2: | 0.78 |
| Area Land Km2: | 0.78 |
| Area Water Km2: | 0.00 |
| Population As Of: | 2020 |
| Population Footnotes: | [2] |
| Population Total: | 231 |
| Population Density Sq Mi: | 764.90 |
| Population Density Km2: | 295.30 |
| Timezone: | Eastern (EST) |
| Utc Offset: | -5 |
| Timezone Dst: | EDT |
| Utc Offset Dst: | -4 |
| Elevation Ft: | 1253 |
| Postal Code Type: | ZIP Code |
| Postal Code: | 16601 (Altoona) |
| Area Code: | 814/582 |
| Blank Name: | FIPS code |
| Blank Info: | 42-49848 |
| Blank1 Name: | GNIS feature ID |
| Blank1 Info: | 2805524 |
Mill Run is an unincorporated community and census-designated place (CDP) in Blair County, Pennsylvania, United States. It was first listed as a CDP prior to the 2020 census.
The CDP is in western Blair County, south of the center of Logan Township. It is bordered to the east by the city of Altoona and is often considered a neighborhood of the city. The community is in the valley of Mill Run, a stream which comes off the Allegheny Front 2miles to the west and flows southeast, then south, to join Beaverdam Creek west of Hollidaysburg. Allegheny Reservoir is just west of the CDP, and Mill Run Reservoir is upstream. Mill Run is part of the watershed of the Frankstown Branch Juniata River, leading to the Susquehanna.