The Lisa was a personal computer designed by Apple Computer, Inc. during the early 1980s. It was the first personal computer to offer a graphical user interface in an inexpensive machine aimed at individual business users.

Development of the Lisa began in 1978 as a powerful personal computer with a graphical user interface (GUI) targeted toward business customers.

In 1982, Steve Jobs was forced out of the Lisa project, so he joined the Macintosh project instead. The Macintosh is not a direct descendant of Lisa, although there are obvious similarities between the systems and the final revision, the Lisa 2/10, was modified and sold as the Macintosh XL.

The Lisa was a more advanced system than the Macintosh of that time in many respects, such as its inclusion of protected memory, cooperative multitasking, a generally more sophisticated hard disk based operating system, a built-in screensaver, an advanced calculator with a paper tape and RPN, support for up to 2 megabytes (MB) of RAM, expansion slots, a numeric keypad, data corruption protection schemes such as block sparing, non-physical file names (with the ability to have multiple documents with the same name), and a larger higher-resolution display. It would be many years before many of those features were implemented on the Macintosh platform. Protected memory, for instance, did not arrive until the Mac OS X operating system was released in 2001. The Macintosh featured a faster 68000 processor (7.89 MHz) and sound. The complexity of the Lisa operating system and its programs taxed the 5 MHz Motorola 68000 microprocessor so that consumers said it felt sluggish, particularly when scrolling in documents.