| Big Run | |
| Name Other: | Tributary to Slippery Rock Creek |
| Map Size: | 300 |
| Pushpin Map: | USA Pennsylvania#USA |
| Pushpin Map Size: | 300 |
| Pushpin Map Caption: | Location of Big Run mouth |
| Subdivision Type1: | Country |
| Subdivision Name1: | United States of America |
| Subdivision Type2: | State |
| Subdivision Name2: | Pennsylvania |
| Subdivision Type3: | County |
| Subdivision Name3: | Butler |
| Subdivision Type4: | Township |
| Subdivision Name4: | Brady |
| Length: | 4.52miles[1] |
| Discharge1 Avg: | 10.36cuft/s at mouth with Slippery Rock Creek[2] |
| Source1: | divide between Big Run and Muddy Creek |
| Source1 Location: | about 0.25 miles south of Elora, Pennsylvania |
| Source1 Coordinates: | 40.9872°N -79.9889°W[3] |
| Source1 Elevation: | 1370feet[4] |
| Mouth: | Slippery Rock Creek |
| Mouth Location: | about 0.25 miles east of Crolls Mills, Pennsylvania |
| Mouth Coordinates: | 41.0206°N -80.0353°W |
| Mouth Elevation: | 1130feet |
| Progression: | Slippery Rock Creek → Connoquenessing Creek → Beaver River → Ohio River → Mississippi River → Gulf of Mexico |
| River System: | Beaver River |
| Tributaries Left: | unnamed tributaries |
| Tributaries Right: | unnamed tributaries |
| Bridges: | William Flynn Highway (PA 8) (x2), Duffy Road, McBride Road |
Big Run is a small tributary of Slippery Rock Creek in western Pennsylvania. The stream rises in northwestern Butler County and flows northwest entering Slippery Rock Creek just east of Crolls Mills, Pennsylvania. The watershed is roughly 26% agricultural, 65% forested and the rest is other uses.[2]