A mimeograph machine was a low-cost duplicating machine that worked by forcing ink through a stencil onto paper. The process was called mimeography, and a copy made by the process was a mimeograph.

Duplicating machines were the predecessors of modern document-reproduction technology. They have now been replaced by digital duplicators, scanners, laser printers and photocopiers, but for many years they were the primary means of reproducing documents for limited-run distribution. The duplicator was pioneered by Thomas Edison and David Gestetner, with Gestetner dominating the market up until the late 1990s.