A preliminary design for an imaging spectrograph that simultaneously covers the 2.15- to 5.2-μm spectral region with a resolution of 0.01 to 0.03 μm is described. The instrument is an extension to two dimensions of an existing infrared spectrograph that uses one-dimensional arrays of infrared detectors. In the two-dimensional version, light entering the spectrograph through a slit is dispersed onto a 256- x 256-pixel InSb array by a novel spherical-faced prism and mirror combination. The use of a prism rather than a grating disperser allows more than a one-octave spectral interval to be covered with no moving parts. In addition, the prism optical efficiency remains high over the entire band covered. The simplicity and ruggedness of the design make it ideal for a space-borne instrument.