The Apple II (sometimes written as Apple ][ or Apple //) was the first mass produced microcomputer and product manufactured by Apple. As one of the earliest and most successful home computers, it is widely attributed as the father of the personal computer industry and what sparked its revolution. Its direct ancestor was the Apple I, a limited production bare circuit board computer for electronics hobbyists which pioneered many features that made the Apple II a commercial success. The Apple II not only was a major technological advancement over its predecessor, the Apple I (in terms of ease of use, features and expandability), it was notably the first to make a strong emphasis on the concept style and visual appeal in order to blend in as a common household appliance. Introduced at the West Coast Computer Faire in 1977, the Apple II was one of the very first successful personal computers and responsible for launching the Apple company into a major business success. Throughout the years a number of different models were introduced and sold, with the most popular model manufactured having relatively minor changes even into the 1990s. By the end of its production in 1993, somewhere between five and six million Apple II series computers (including approximately 1.25 million Apple II GS models) had been produced.

Throughout the 1980s and much of the 1990s, the Apple II was the de facto standard computer in American education; some of them are still operational in classrooms today. The Apple II was popular with business users as well as with families and schools, particularly after the release of the first-ever personal computer spreadsheet, VisiCalc, which initially ran only on the Apple II.

The original Apple II operating system was only the built-in BASIC interpreter contained in ROM. Apple DOS was added to support the diskette drive; the last version was "Apple DOS 3.3". Apple DOS was superseded by ProDOS to support a hierarchical filesystem and larger storage devices. Using a diskette or hard-disk, the Apple II could also load the UCSD Pascal operating system. P-System binaries are compatible with a large number of other computers, including the original IBM Personal Computer. With an optional Z80 based expansion card the Apple II could even run the popular Wordstar and dBase software under the CP/M operating system. At the height of its evolution, towards the late 1980s, the platform had evolved into a hybrid of the Apple II and Macintosh with the introduction of the Apple II GS . With 16-bit processing capabilities, a mouse driven Graphical User Interface along with graphic and sound capabilities far beyond the original, the Apple II had appeared to have a promising future and vast potential. Apple, however, decided to abandon this direction and focus on the Macintosh instead, despite strong sales and popularity.

After years of focus on Apple's Macintosh product line, it finally eclipsed the Apple II series in the early 1990s. Even after the introduction of the Macintosh, the Apple II had remained Apple's primary revenue source for years: the Apple II and its associated community of third-party developers and retailers were once a billion-dollar-a-year industry. The Apple II GS model was sold through to the end of 1992. The Apple IIe model was removed from the product line on October 15, 1993, ending an era.