Unix started out around 1969 as an operating system for minicomputers at AT&T Bell Labs. AT&T first licensed it to educational institutions, then to commercial users.

Over the years, many companies and institutions made their own version of Unix, either by adapting AT&T code or by writing replacements with the same interfaces: bsd, Xenix/sco, sunos/solaris, hp-ux, aix, minix, NextSTEP, osf1, linux, ...

This tag is only about the historical product known as UNIX Time-Sharing System or UNIX System III/IV/V. For the history of the Unix family of operating systems in general, use the tag history.