Lisa is a desktop computer developed by Apple, produced from January 19, 1983 to August 1, 1986, and succeeded by Macintosh. It was the first mass-market personal computer operable through a graphical user interface (GUI). In 1983, a machine like the Lisa was still so expensive that it was primarily marketed to individual and small and medium-sized businesses as a groundbreaking new alternative to much bigger and more expensive mainframes or minicomputers such as from IBM, that either require additional, expensive consultancy from the supplier, hiring specially trained personnel, or at least, a much steeper learning curve to maintain and operate.

Development of project "LISA" began in 1978. It underwent many changes and shipped at US$9,995 (equivalent to $31,600 in 2024) with a five-megabyte hard drive. It was affected by its high price, insufficient software, unreliable FileWare (codename Twiggy) floppy disks, and the imminent release of the cheaper and faster Macintosh. Only 60,000 Lisa units were sold in two years.

Lisa was considered a commercial failure but with technical acclaim, introducing several advanced features that reappeared on the Macintosh and eventually IBM PC compatibles. These include an operating system with memory protection and a document-oriented workflow. The hardware is more advanced overall than the following Macintosh, including hard disk drive support, up to 2 megabytes (MB) of random-access memory (RAM), expansion slots, and a larger, higher-resolution display.

Lisa's CPU and the storage system were strained by the complexity of the operating system and applications, especially its office suite, and by the ad hoc protected memory implementation, due to the lack of a Motorola memory management unit. Cost-cutting measures that target the consumer market, and the delayed availability of the 68000 processor and its impact on the design process, made the user experience sluggish. The workstation-tier high price and lack of a technical software application library made it a difficult sale for all markets. The IBM PC's popularity and Apple's decision to compete with itself through the lower-priced Macintosh also hindered Lisa's acceptance.

In 1981, after Steve Jobs was forced out of the Lisa project by Apple's board of directors, he appropriated the Macintosh project from Jef Raskin, who had conceived it as a sub-$1,000 (equivalent to $4,300 in 2024) text-based appliance computer in 1979. Jobs immediately redefined Macintosh to be graphical, but as a less expensive and more focused alternative to Lisa.

Macintosh's launch in January 1984 quickly surpassed Lisa's underwhelming sales. Jobs began assimilating increasing numbers of Lisa staff, as he had done with the Apple II division upon taking Raskin's project. Newer Lisa models addressed its shortcomings but, even with a major price reduction, the platform failed to achieve sales volumes comparable to the much less expensive Mac. The Lisa 2/10 is the final model, then rebranded as the high-end Macintosh XL.

Though the original documentation only refers to it as "The Lisa", Apple officially stated that the name was an acronym for "Local Integrated Software Architecture". Because Steve Jobs's first daughter was named Lisa (born in 1978), it was sometimes inferred that the name also had a personal association, and perhaps that the acronym was a backronym contrived later to fit the name. Andy Hertzfeld said that the acronym was reverse-engineered from the name "Lisa" in late 1982 by the Apple marketing team after they had hired a marketing consultancy firm to find names to replace "Lisa" and "Macintosh" (at the time considered by Jef Raskin to be merely internal project codenames) and then rejected all of the suggestions. Privately, Hertzfeld and the other software developers used "Lisa: Invented Stupid Acronym", a recursive backronym, and computer industry pundits coined the term "Let's Invent Some Acronym" to fit Lisa's name. Decades later, Jobs told his biographer Walter Isaacson: "Obviously it was named for my daughter."

The project began in 1978 as an effort to create a more modern version of the then-conventional design epitomized by the Apple II. A ten-person team occupied its first dedicated office at 20863 Stevens Creek Boulevard next to the Good Earth restaurant, and nicknamed "the Good Earth building". Initial team leader Ken Rothmuller was soon replaced by John Couch, under whose direction the project evolved into the "window-and-mouse-driven" form of its eventual release. Trip Hawkins and Jef Raskin contributed to this change in design. Apple's co-founder Steve Jobs was involved in the concept.