Petrolia
- County:
- Butler County
- County Seat:
- No
- Area (mi²):
- 0.395
- State:
- Pennsylvania
Petrolia is a borough located in Butler County, Pennsylvania. Petrolia has a 2026 population of 173. Petrolia is currently declining at a rate of -0.57% annually and its population has decreased by -3.35% since the most recent census, which recorded a population of 179 in 2020.