The Haynesville Shale is a rock formation mainly composed of consolidated clay-sized particles deposited and buried in northwest Louisiana and east Texas. It is characterized by ultra-low permeability but has a high porosity compared to other shales.

The Haynesville Shale came into prominence in 2008 as a potentially major shale gas resource. Producing natural gas from the Haynesville Shale involves drilling wells from 10,000 feet (3,000 m) and to 13,000 feet (4,000 m) deep. The formation is deeper in areas nearer the Gulf of Mexico. The Haynesville Shale has recently been estimated to be the largest natural gas field in the lower 48 with an estimated 250 trillion cubic feet of recoverable gas. Production has boomed since late March 2008 and is centered in the Shreveport, Louisiana area.