A two‐dimensional, ultraviolet photon‐counting detector suitable for spaceflight use, consisting of a microchannel plate intensifier coupled to a Reticon photodiode array, has been constructed and tested. The design is an extension of the one‐dimensional detector flown on theHopkinsUltravioletTelescope. Extensive laboratory measurements have determined the operating characteristics of the detector and shown that it can successfully centroid with subdiode resolution. It was flown as part of an ultraviolet spectrometer on two sounding rockets, and successfully obtained long slit spectra of Comet Austin (1990 V) and the Io plasma torus surrounding Jupiter in the wavelength range of 1150–1850 A˚. Details of the design, construction, testing, and flight performance of the detector are presented.