The Motorola 68000 (sometimes shortened to Motorola 68k or m68k and usually pronounced "sixty-eight-thousand") is a 16/32-bit complex instruction set computer (CISC) microprocessor, introduced in 1979 by Motorola Semiconductor Products Sector.

The design implements a 32-bit instruction set, with 32-bit registers and a 16-bit internal data bus. The address bus is 24 bits and does not use memory segmentation, which made it easier to program for. Internally, it uses a 16-bit data arithmetic logic unit (ALU) and two 16-bit arithmetic units used mostly for addresses, and has a 16-bit external data bus. For this reason, Motorola termed it a 16/32-bit processor.

As one of the first widely available processors with a 32-bit instruction set, large unsegmented address space, and relatively high speed for the era, the 68k was a popular design through the 1980s. It was widely used in a new generation of personal computers with graphical user interfaces, including the Macintosh 128K, Amiga, Atari ST, and X68000, as well as video game consoles such as the Sega Genesis/Mega Drive console. Several arcade game systems also used the 68000.

Later processors in the Motorola 68000 series, beginning with the Motorola 68020, use full 32-bit ALUs and have full 32-bit address and data buses, speeding up 32-bit operations and allowing 32-bit addressing, rather than the 24-bit addressing of the 68000 and 68010 or the 31-bit addressing of the Motorola 68012. The original 68k is generally software forward-compatible with the rest of the line despite being limited to a 16-bit wide external bus.

Although the processors are no longer in production, functionally-identical clones and reproductions of the 68000 are still actively made.

Motorola's first widely produced microprocessor was the 6800, introduced in early 1974 and available in quantity late that year. The company set itself the goal of selling 25,000 units by September 1976, a goal they did meet. Although a capable design, it was eclipsed by more powerful designs, such as the Zilog Z80, and less expensive designs, such as the MOS Technology 6502. By late 1976, the sales book was flat and the division was only saved by a project for General Motors that turned into a huge product line for engine control and other tasks.

By the time the 6800 was introduced, a small number of 16-bit designs had come to market. These were generally modeled on minicomputer platforms like the Data General Nova or PDP-11. Based on the semiconductor manufacturing processes of the era, these were often multi-chip solutions like the National Semiconductor IMP-16, or the single-chip PACE that had issues with speed.

With the sales prospects for the 6800 dimming, but still cash-flush from the engine control sales, in late 1976 Colin Crook, Operations Manager, began considering how to successfully win future sales. They were aware that Intel was working on a 16-bit extension of their 8080 series, which would emerge as the Intel 8086, and had heard rumors of a 16-bit Zilog Z80, which became the Z8000. These would use new design techniques that would eliminate the problems seen in earlier 16-bit systems.