Original Equipment Manufacturer (OEM) is a company that makes a part or subsystem that is used in another company's end product. For example, if Acme Manufacturing Co. makes power cords that are used on IBM computers, Acme is the OEM.

However, the term is used in several other ways, which causes ambiguity. It sometimes refers to the maker of a system that includes other companies' subsystems, an end-product producer, an automotive part that is manufactured by the same company that produced the original part used in the automobile's assembly, or a value-added reseller.