The Atari 800 was released in late 1979 alongside the low-end Atari 400 as Atari's first entries in the then-new home computer market. It had much greater expansion capabilities over the 400, with several expansion slots hidden behind a removable top cover. Officially the 800 could be expanded with up to 48 KB of RAM, with later 800s being shipped fully loaded. It also had a proper full-travel keyboard and a monitor port which offered better video quality than RF. The 800 was also the only Atari 8-bit computer to have two cartridge ports, though almost all cartridges only plugged into the left port, with the right port only having a handful of third-party utilities released for it.

Atari attempted to replace the 800 with the 1200XL in 1983, but the 1200XL was not well-received and was swiftly discontinued after just a few months. The 800 was finally replaced by the 800XL later in 1983.