A pressure cooker is a container with an airtight lid that traps steam from boiling water; the steam increases pressure inside the cooker, which raises the water's boiling point. The higher temperature cooks food much faster than usual. The pressure cooker includes a safety valve to prevent explosion if the steam pressure gets too high.

Both the device and the valve were invented in 1679 by the French physician Denis Papin, who called it a "steam digester." He demonstrated his invention to the Royal Society by reducing bones to an edible jelly. Papin described his "New Digester" in a 1681 pamphlet, emphasizing the fact that food cooked under pressure in this way retains flavor, color, and nutritive value that otherwise would be lost. In spite of these advantages, Papin's "digester" was used less for cooking than as an autoclave--a vessel that uses the high temperatures produced by steam under pressure to rapidly sterilize medical and scientific materials, an application in standard use today.

After the United States Department of Agriculture announced in 1917 that pressure cooking was the only safe way to preserve low-acid foods, home pressure cookers came on the market, but these were at first large and cumbersome to use. After World War II, many manufacturers began producing home devices, and pressure cooking became much more common. Today, pressure cooking methods are also used to cook wood chips so they become wood pulp that can be used to manufacture paper.