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Unisys Corporation is a technology company, previously specialising purely in computer hardware but currently more of a services firm. The company employs around 38,000 people and in 2001 the company had a profit of $1.65 bn on revenues of $6.02 bn. It is headquartered in Blue Bell, Pennsylvania.

It was formed in September 1986 through the merger of the mainframe corporations Sperry and Burroughs, so-called dinosaur mating, with Burroughs buying Sperry for $4.8 bn. The name was chosen after an internal competition. The merger was the largest in the computer industry at the time and made Unisys the second largest computer company, with income of $10.5 bn. In 1988 the company acquired Convergent Technologies, and their innovative CTOS.

Important events in the company's history include the development of the 2200 series from 1986, including the UNISYS 2200/500 CMOS mainframe, and the Micro A in 1989, the first desktop mainframe.

Unisys has become more known due to its single patent on the LZW algorithm than for any other reason. The algorithm is used in the GIF file format. At the end of December 1994, CompuServe and Unisys announced that the U.S. patent which Unisys holds for the LZW compression algorithm would be enforced for GIFs: all commercial programs capable of producing GIF files would be required to pay a license fee to Unisys. By this time, GIF was in such widespread use that most companies producing these programs had little choice but to pay up. These problems led to the development of the PNG format, which has become the third common image format on the Web. In late August 1999, Unisys terminated its royalty-free LZW technology licenses for free software and non-commercial proprietary software and even for individual users of unlicensed programs, prompting the League for Programming Freedom to launch the Burn All GIFs campaign to inform the public of the alternatives. The patent expired on June 20, 2003 in the United States.

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Note: bn. means billion.