Lisa is a desktop computer developed by Apple, released on January 19, 1983. It is one of the first personal computers to present a graphical user interface (GUI) in a machine aimed at individual business users. Development of the Lisa began in 1978, and it underwent many changes during the development period before shipping at US$9,995 (equivalent to $25,970 in 2020) with a five-megabyte hard drive. Lisa was affected by its high price, insufficient software, unreliable Apple FileWare floppy disks, and the immediate release of the cheaper and faster Macintosh. Only 10,000 Lisas were sold in two years.

Considered a commercial failure (albeit one with technical acclaim), Lisa introduced a number of advanced features that would later reappear on the Macintosh and eventually IBM PC compatibles. Among these is an operating system with protected memory and a document-oriented workflow. The hardware was more advanced overall than the forthcoming Macintosh 128K; the Lisa included hard disk drive support, capacity for up to 2 megabytes (MB) of random-access memory (RAM), expansion slots, and a larger, higher-resolution display.

The complexity of the Lisa operating system and its associated programs (most notably its office suite), as well as the ad hoc protected memory implementation (due to the lack of a Motorola MMU), placed a high demand on the CPU and, to some extent, the storage system as well. As a result of cost-cutting measures designed to bring the system more into the consumer bracket, advanced software, and factors such as the delayed availability of the 68000 and its impact on the design process, Lisa’s user experience feels sluggish overall. The workstation-tier price (albeit at the low end of the spectrum at the time) and lack of a technical software application library made it a difficult sell for much of the technical workstation market. Compounding matters, the runaway success of the IBM PC and Apple's decision to compete with itself, mainly via the lower-cost Macintosh, were further impediments to platform acceptance.

In 1982, after Steve Jobs was forced out of the Lisa project by Apple’s Board of Directors, he then appropriated the Macintosh project from Jef Raskin, who had originally conceived of a sub-$1,000 text-based appliance computer in 1979. Jobs immediately redefined Macintosh as a less expensive and more focused version of the graphical Lisa.

When Macintosh launched in January 1984, it quickly surpassed Lisa’s sluggish sales. Jobs then began assimilating increasing numbers of Lisa staff, as he had done with the Apple II division after assuming control over Raskin’s project. Newer Lisa models were eventually introduced to address its shortcomings but, even after lowering the list price considerably, the platform failed to achieve favorable sales numbers compared to the much less expensive Mac. The final model, the Lisa 2/10, was rebranded as the Macintosh XL to become the high-end model in the Macintosh series.