An MFX file is a font file used by the Maxis SimCity 4 simulation game. It is used to render game text on screen from one of the selected font types including Arial, Courier, or any other font available in the font file. MFX files come installed with the SimCity 4 game and need not be created manually.
SimCity 4 is a simulation computer game for creating city-building simulations. Maxis, the developer of SimCity, is a subsidiary of Electronic Arts. The game was initially launched in January, 2003.