The wide-field infrared explorer (WIRE) is a small spaceborne telescope specifically designed to study the evolution of starburst galaxies. This powerful astronomical instrument will be capable of detecting typical starburst galaxies at a redshift of 0.5, ultraluminous infrared galaxies beyond a redshift of 2, and luminous protogalaxies beyond a redshift of 5. The WIRE survey, to be conducted during a four month period during 1998, will cover over 100 deg2 of high galactic latitude sky at 12 and 25 micrometer. WIRE will measure the ratio of 12 and 25 micrometer flux of detected sources, which is a powerful statistical luminosity indicator. The distribution of starburst galaxy 12-25 micrometer colors as a function of flux density will reveal their evolutionary history and perhaps the presence of protogalaxies at high redshifts. This mission, which is part of the NASA Small Explorer program, takes advantage of recent advances in infrared array detector technology to provide a large sensitivity gain over previously flown missions. During its four-month mission lifetime, WIRE will amass a catalog exceeding the size of the 1983 Infrared Astronomy Satellite (IRAS) Point Source Catalog at flux levels over 500 times fainter than the IRAS Faint Source Catalog. WIRE has been designed to maximize detections of high-redshift starburst galaxies using an extremely small and simple instrument. The 30 cm aperture Cassegrain telescope has no moving parts, no reimaging optics and a wide 33 by 33 arcminute field of view. The optics and detectors are cooled during the mission using a lightweight two-stage solid hydrogen cryostat. The three-axis stabilized spacecraft bus is provided by the Goddard Space Flight Center Small Explorer Project Team. The mission, to be launched in September 1998 using an Orbital Sciences Corporation Pegasus XL Launch Vehicle, is managed by GSFC.