Mon is a generic Japanese term for gate often used, either alone or as a suffix, in referring to the many gates used by Buddhist temples, Shinto shrines and traditional-style buildings and castles.

A gate or gateway is a point of entry to or from a space enclosed by walls. The word derived from old Norse "gat" meaning road or path; But other terms include yett and port. The concept originally referred to the gap or hole in the wall or fence, rather than a barrier which closed it. Gates may prevent or control the entry or exit of individuals, or they may be merely decorative. The moving part or parts of a gateway may be considered "doors", as they are fixed at one side whilst opening and closing like one.