Waynesburg is a borough in and the county seat of Greene County, Pennsylvania, United States, about 50 miles south of Pittsburgh. Its population was 4,006 at the 2020 census. The region around Waynesburg is underlaid with several layers of coking coal, including the Pittsburgh No. 8 seam, the Waynesburg seam, and the Sewickley seam. The area is also rich with coalbed methane, which is being developed from the underlying Marcellus Shale, the largest domestic natural gas reserve.