In internal combustion engines, a poppet valve (also sometimes called mushroom valve) is a valve typically used to control the timing and quantity of petrol (gas) or vapour flow into or out of an engine, but with many other applications.

It consists of a hole or open-ended chamber, usually round or oval in cross-section, and a plug, usually a disk shape on the end of a shaft known as a valve stem. The working end of this plug, the valve face,