The Sinclair ZX80 is a home computer launched on 29 January 1980 by Science of Cambridge Ltd. (later to be better known as Sinclair Research). It is notable for being one of the first computers available in the United Kingdom for less than a hundred pounds. It was available in kit form for £79.95, where purchasers had to assemble and solder it together, and as a ready-built version at £99.95.

The ZX80 was very popular straight away, and for some time there was a waiting list of several months for either version of the machine.

The ZX80, named after the Z80 processor, was designed by Jim Westwood. It featured a 3.25 MHz Z80 CPU, 1 KB of static RAM, and 4 KB of ROM. The machine had no sound output and used a simple RF connection to display on a household television. Video output was black-and-white and character-based. The firmware contained the Sinclair BASIC programming language, editor, and operating system. The only means of expansion was a slot opening at the rear of the case, which exposed an expansion bus edge connector.

The ZX80 was advertised as the first personal computer for under £100 and received praise for its value and documentation. However, it faced criticism for screen blanking during program execution, small RAM size, and the keyboard design. Sales reached around 50,000, and the UK led the world in home computer ownership during the 1980s. Original ZX80s in good condition are now sought after by collectors. Clones of the ZX80 include the MicroAce, NE-Z80, and the Microdigital TK80.