IXI Limited was a British software company that developed and marketed windowing products for Unix, supporting all the popular Unix platforms of the time. Founded in 1987, it was based in Cambridge. The product it was most known for was X.desktop, a desktop environment graphical user interface built on the X Window System. IXI was acquired by the Santa Cruz Operation (SCO) in February 1993.

In the beginning of the 1970s, the so-called Cambridge hi-tech cluster became the site of a network of new firms in the rapidly growing computer field, many of which featured founders and employees who had studied at the University of Cambridge. And in particular, as an article in the journal Regional Studies has noted, IXI was one of many companies started by founders or employees or those in the nexus of Cambridge-based Acorn Computers, the most noted of which is ARM Holdings.

IXI founder Ray Anderson was a graduate of the university who had become director of research and development at Torch Computers, a computer systems firm located in the Cambridge area that was most known for making peripherals for the BBC Micro made by Acorn. Torch built workstations among its products, and also had a license agreement to provide NeXT with aspects of workstation technology.

In the end, Torch was not successful, but its work inspired Anderson to carry the idea on.

IXI Limited was founded by Ray Anderson in 1987 as a private company. Anderson originally had a former colleague as a partner, but the partner decided a start-up was too uncertain and pulled out within a year or so. Anderson found funding for IXI from sources in the United Kingdom, Germany, Austria, and Japan, but avoiding US investors as his prior experiences had made him leery of them.

As one former SCO UK employee has succinctly summarised, "IXI specialised in software that ran on Unix and made Unix easier to use." In particular, a goal was to make Unix workstations as easy to use as a Macintosh, which would allow non-technical people to use such platforms. IXI's best-known product was X.desktop, an X11-based graphical desktop environment with finder and file management capabilities for Unix systems. There was an opportunity for such a product because when the X11 version of the X Window System came out in 1987, it made a point of separation of mechanism and policy (indeed, it has been termed a canonical example of that design philosophy). Consequently, while it supported the ability to provide such things, it contained no specification for application user-interface design such as buttons, menus, or window title-bar styles, nor did it provide a standard window manager, file manager, or desktop.

The initial unreleased version of X.desktop, intended as a proof of concept, was programmed to the Xlib level; the first version that saw public release, 1.3, was based on the Xt library and Athena widgets. The X.desktop product then came to be based on Motif toolkit from the Open Software Foundation (OSF), a switch that happened in 1989 with release 2.0.

The first customers for IXI came in the financial industry, who were early adopters of Unix-based workstations. These were generally American companies, with sales to the Japanese market coming soon thereafter. Indeed, IXI has been characterized as an example of a "global start-up", in that instead of following the expected route for a start-up of establishing a domestic business first and then slowly expanding into international operations, it worked to establish an international business right away.