KornShell (ksh) is a Unix shell which was developed by David Korn at Bell Labs in the early 1980s and announced at USENIX on July 14, 1983.

[7] Other early contributors were Bell Labs developers Mike Veach and Pat Sullivan, who wrote the Emacs and vi-style line editing modes' code, respectively.

The functionality of the original KornShell, ksh88, was used as a basis for the standard POSIX.2, Shell and Utilities, Command Interpreter (IEEE Std 1003.2-1992).

[18] In March 2020, AT&T decided to roll back the community changes, stash them in a branch, and restart from ksh93u+, as the changes were too broad and too ksh-focused for the company to absorb into a project in maintenance mode.

[23] For the purposes of the lists below, the main software branch of KSH is defined as the original program, dating from July 1983, up and through the release of KSH2020 in late 2019.

Continuing development of follow-on versions (branches) of KSH have split into different groups starting in 2020 and are not elaborated on below.