The Barnett Shale is a geological formation of economic significance. It consists of sedimentary rocks of Mississippian age (354-323 million years ago) in the State of Texas. The formation is estimated to stretch from the city of Dallas to west of the city of Fort Worth and south, covering 5,000 square miles and at least 17 counties. The Barnett Shale is already the second largest producing on-shore domestic natural gas field in the United States

Some experts have suggested the Barnett Shale may be the largest onshore natural gas field in the United States. The field is proven to have 2.5 trillion cubic feet of natural gas, and is widely estimated to contain as much as 30 trillion cubic feet of natural gas resources.