SAOimage (pronounced S-A-0-image), is an X windows-based interactive program to display astronomical image data on a workstation screen. SAOimage was developed by the author and funded by NASA as part of the Smithsonian Astrophysical Observatory's PROS analysis software package for the U.S. ROSAT Science Data Center. It can run either stand-alone, reading FITS (SIMPLE=T), IRAF (.imh), and array image files directly, or be connected to IRAF, emulating NOAO's imtool, for interactive image display and analysis. Originally developed for X10, under the name "ximage", SAOimage now uses X1l and compatible display servers and runs under UNIX (SYSV and BSD) or VMS. (The VMS port was done by Jay Travisano of the Space Telescope Science Institute.)