Greene County is a county in the Commonwealth of Pennsylvania. As of the 2020 census, the population was 35,954. Its county seat is Waynesburg. Greene County was created on February 9, 1796, from part of Washington County and named for General Nathanael Greene. The county is part of the Southwest Pennsylvania region of the state.

Waynesburg is a borough in and the county seat of Greene County, Pennsylvania, United States, about 50 miles (80 km) south of Pittsburgh. Its population was 4,006 at the 2020 census.