The Apple IIGS (stylized as IIgs) is the fifth and most powerful model in the Apple II series of personal computers produced by Apple Computer. The "GS" in the name stands for Graphics and Sound, referring to its enhanced multimedia capabilities, especially its state-of-the-art sound and music synthesis, which greatly surpassed previous models of the line and most contemporary machines like the Macintosh and IBM PC.

The machine was a radical departure from any previous Apple II, with its true 16-bit architecture, increased processing speed, direct access to megabytes of RAM, wavetable music synthesizer, graphical user interface, and mouse. While still maintaining full backwards compatibility with earlier Apple II models, it blended the Apple II and aspects of Macintosh technology into one. Keeping with Apple's "Apple II Forever" slogan of the time, the IIGS set forth a promising future and evolutionary advancement of the Apple II line, but Apple paid it relatively little attention as the company increasingly focused on the Macintosh platform.

The Apple IIGS was the first computer produced by Apple to use a color graphical user interface, as well as the "Platinum" (light grey) color scheme and the Apple Desktop Bus interface for keyboards, mice, and other input devices. It was also the first personal computer to come with a built-in "wavetable" sample-based synthesizer chip, utilizing technology from Ensoniq. The machine outsold all other Apple products, including the Macintosh, during its first year in production.

The IIGS was released September 15, 1986. Apple's portion of the computer industry at this time was transitioning from the 8-bit 6502 CPU technology that started it, to the newer 16/32 bit Motorola 68000 used by computers such as the Commodore Amiga and Atari ST and the Apple Macintosh. In order to maintain compatibility with previous members of the Apple II line, Apple chose the Western Design Center 65C816 processor for the IIgs. In addition to providing platform continuity, the lower capability processor kept the IIgs from competing with the Macintosh which, at the time, was monochrome-only. Like the Apple IIe, the IIgs was somewhat popular with schools, but Apple failed to promote and update the IIGS, preferring to focus on introducing the Macintosh into these markets instead. The IIGS was far more expensively priced and slower in terms of raw processing speed compared to its competitors and increasingly, without regular advancement updates, fell behind other personal computers over its lifetime. Apple finally ceased production of the model in December 1992.