'''Unix System Laboratories''' (USL), sometimesproperly written as '''UNIX System Laboratories''' per guidelines of [[The Open Group]], owner of the UNIX trademark, was an American software laboratory and product development company that existed from 1989 through 1993. At first wholly, and then majority, owned by [[AT&T Corporation|AT&T]], it was responsible for the development and maintenance of one of the main branches of the [[Unix]] [[operating system]], the [[SVR4|UNIX System V Release 4]] source code product. Through [[Univel]], a partnership with [[Novell]], it was also responsible for the development and production of the [[UnixWare]] packaged operating system for [[IA-32|Intel architecture]]. In addition it developed [[Tuxedo (software)|Tuxedo]], a [[Transaction processing system|transaction processing monitor]], and was responsible for certain products related to the [[C++ programming language]]. USL was based in [[Summit, New Jersey]], and its CEOs were Larry Dooling followed by [[Roel Pieper]].
Created from earlier AT&T entities, USL was, as industry writer Christopher Negus has observed, the culmination of AT&T's long involvement in Unix, "a jewel that couldn't quite find a home or a way to make a profit."<ref name="negus"/> USL was sold to Novell in 1993.
