XEphem is a Motif based ephemeris and planetarium program for Unix-like operating systems developed by Elwood C. Downey.

[citation needed] Its commercial edition was discontinued in 2016; the free version continued to be offered as proprietary software.

[3] In 2021, however, Downey relicensed XEphem's source code under the MIT License, raising the release version from 3.7.7 to 4.0.0 to highlight the change.

[7] XEphem is a client for Internet data sources such as the Digitized Sky Survey, Solar and Heliospheric Observatory, AAVSO light curves, and global temperature and cloud coverage.

[9] XEphem can also read several astrometric catalogs in their original formats: Numerical routines are used in PyEphem with permission of Elwood Downey.