Hydraulic fracturing is a method used to create fractures that extend from a borehole into rock formations, which are typically maintained by a proppant. The method is informally called fracing. The technique is used to increase or restore the rate which fluids, such as oil, gas or water, can be produced from the formation. By creating or restoring fractures, the surface area of the formation exposed to the borehole is increased, which effectively increases the rate that fluids can be produced from the reservoir formations.

The main industrial use of hydraulic fracturing is in stimulating production from oil and gas wells. Hydraulic fracturing is also applied to stimulating groundwater wells, preconditioning rock for caving or inducing rock to cave in mining, as a means of enhancing waste remediation processes (usually hydrocarbon waste or spills), to dispose of waste by injection into suitable deep rock formations, and as a method to measure the stress in the earth. Volcanic dikes and sills are examples of natural hydraulic fractures. Hydraulic fracturing incorporates results from the disciplines of fracture mechanics, fluid mechanics, solid mechanics, and porous medium flow.