A pressure vessel is a container designed to hold gases or liquids at a pressure substantially different from the ambient pressure. Design involves parameters such as maximum safe operating pressure and temperature, safety factor, corrosion allowance and minimum design temperature (for brittle fracture).

Pressure vessels can theoretically be almost any shape, but shapes made of sections of spheres, cylinders, and cones are usually employed. A common design is a cylinder with end caps called heads. Head shapes are frequently either hemispherical or dished (torispherical).

Pressure vessels are used in a variety of applications in both industry and the private sector. They appear in these sectors as industrial compressed air receivers and domestic hot water storage tanks. Other examples of pressure vessels are filter housings, strainer housings, and many other vessels in mining operations, oil refineries and petrochemical plants, hydraulic reservoirs under pressure and storage vessels for liquefied gases such as ammonia, chlorine, and LPG (propane, butane).