Xterm is a terminal emulator and now part of the X Window System. A user can start any number of instances of xterm on the same screen (X display), each instance is then that in their current process a simulated terminal. Frequently xterm is used to represent and interaction used with a Unix shell.

Originally xterm was developed as a stand-alone terminal for the VS100 by Mark Vandevoorde, a student of Jim Gettys, in the summer of 1984. Xterm is thus slightly older than X itself soon became clear that it was more appropriate to xterm to develop as part of X and not as an independent project. For this reason it was soon taken up in this after the formation of the X project.

After many years as part of X, the line of development around 1996 to the XFree86 project moved (which was working with the version X11R6.3 ) and is currently maintained by Thomas Dickey.

Since the time of the first console version many different variants have been developed. A known variant with reference to xterm is rxvt. In the best-known desktop environments for the X Window System xterm for example by console ( KDE ) or gnome-terminal was displaced ( in GNOME).