Abstract: The Miniature Fourier Transform Spectrophotometer provides the capability, in a miniaturized device, of determining the light absorption/transmission spectra of a collected sample of gas or liquid though Fourier Transform spectroscopy techniques. The device takes an optical input from an optical fiber, manipulates that light through miniature optical components, and launches it into a miniaturized Michelson interferometer with a scanning mirror that acquires the interferogram of the optical input. The interferogram can be processed to retrieve the spectrum of the input light. A novel multi-stepped micro-mirror operates as the optical path length modulator in the miniaturized interferometer. A unique monolithic beamsplitter/mirror combination provides for accurate alignment of the components and greatly simplifies product integration. The device is designed to cover various optical spectra of interest.