GORE-TEX is a waterproof/breathable fabric and a registered trademark of W.L. Gore & Associates. It was co-invented by Wilbert L. Gore (1912-1986), Rowena Taylor, and Gore's son, Robert W. Gore for use in space.

Robert Gore was granted U.S. Patent 3,953,566 on April 27, 1976, for a porous form of polytetrafluoroethylene with a micro-structure characterized by nodes interconnected by fibrils.

Gore-Tex materials are typically based on thermo-mechanically expanded polytetrafluoroethylene (PTFE) and other fluoropolymer products. They are used in a wide variety of applications such as high performance fabrics, medical implants, filter media, insulation for wires and cables, gaskets, and sealants. But Gore-Tex is best known for its use in protective rain wear.

The simplest sort of rain wear is a two layer sandwich. The outer layer is typically nylon or polyester and provides strength. The inner one is polyurethane, aka PU, and provides water resistance, at the cost of breathability.

Early Gore-Tex fabric replaced the inner layer of PU with a thin, porous fluoropolymer membrane (Teflon) with a polyurethane coating that is bonded to a fabric, usually nylon or polyester.

This membrane had about 9 billion pores per square inch (around 1.4 billion pores per square centimeter), each of which is approximately 1/20,000 the size than a water droplet, making it impenetrable to liquid water while still allowing the smaller sized water vapour to pass through.

However it was found that when used in clothing the exposed Teflon membrane layer was easily damaged, as well as being compromised by exposure to the wearer's own sweat. As a result a third layer was added - a coating of PU on the inside of the fabric to protect the membrane. This final design has been criticised as offering greatly reduced performance and more marketing benefits than performance ones.