The Atari ST is a line of personal computers from Atari Corporation and the successor to the Atari 8-bit family. The initial model, the Atari 520ST, had limited release in April–June 1985 and was widely available in July. It was the first personal computer with a bitmapped color GUI, using a version of Digital Research's GEM from February 1985. The Atari 1040ST, released in 1986 with 1 MB of RAM, was the first home computer with a cost-per-kilobyte of less than US$1.

"ST" officially stands for "Sixteen/Thirty-two", referring to the Motorola 68000's 16-bit external bus and 32-bit internals. The system was designed by a small team led by Shiraz Shivji. Alongside the Macintosh, Amiga, Apple IIGS, and Acorn Archimedes, the ST is part of a mid-1980s generation of computers with 16- or 32-bit processors, 256 KB or more of RAM, and mouse-controlled graphical user interfaces.

The ST was sold with either Atari's color monitor or less expensive monochrome monitor. Color graphics modes were available only on the former while the highest-resolution mode required the monochrome monitor. Some later models could display the color modes on a TV.

In some markets, particularly Germany, the ST gained a foothold for CAD and desktop publishing. With its built-in MIDI ports, it was popular for music sequencing and as a controller of musical instruments among amateurs and professional musicians.

It was superseded by the Atari STE, Atari TT, Atari MEGA STE and Falcon computers.

Atari () is a brand name that has been owned by several entities since its inception in 1972. It is currently owned by French publisher Atari SA through a subsidiary named Atari Interactive. The original Atari, founded in Sunnyvale, California, in 1972 by Nolan Bushnell and Ted Dabney, was a pioneer in arcade games, home video game consoles and home computers. The company's products, such as Pong and the Atari 2600, helped define the electronic entertainment industry from the 1970s to the mid-1980s.

In 1984, as a result of the video game crash of 1983, the home console and computer divisions of the original Atari Inc. were sold off, and the company was renamed Atari Games Inc. Atari Games received the rights to use the logo and brand name with appended text "Games" on arcade games, as well as rights to the original 1972–1984 arcade hardware properties. The Atari Consumer Electronics Division properties were in turn sold to Jack Tramiel's Tramel Technology Ltd., which then renamed itself to Atari Corporation. In 1996, Atari Corporation reverse-merged with disk-drive manufacturer JT Storage (JTS), becoming a division within the company. In 1998, Hasbro Interactive acquired all Atari Corporation related properties from JTS, creating a new subsidiary, Atari Interactive.

Infogrames Entertainment (IESA) bought Hasbro Interactive in 2001 and renamed it Infogrames Interactive, which intermittently published Atari-branded titles. In 2003, it renamed the division Atari Interactive. Another IESA division, Infogrames Inc., changed its name to Atari the same year, licensing the Atari name and logo from its fellow subsidiary.

In 2008, IESA completed its acquisition of Atari, Inc.'s outstanding stock, making it a wholly owned subsidiary. IESA renamed itself Atari SA in 2009. It sought bankruptcy protection under French law in January 2013.

As of 2022, the current Atari is pursuing several lines of business outside of video gaming, including cryptocurrency and video-game themed hotels.

The Atari 2600, initially branded as the Atari Video Computer System (Atari VCS) from its release until November 1982, is a home video game console developed and produced by Atari, Inc. Released in September 1977, it popularized microprocessor-based hardware and games stored on swappable ROM cartridges, a format first used with the Fairchild Channel F in 1976. The VCS was bundled with two joystick controllers, a conjoined pair of paddle controllers, and a game cartridge—initially Combat and later Pac-Man.

Atari was successful at creating arcade video games, but their development cost and limited lifespan drove CEO Nolan Bushnell to seek a programmable home system. The first inexpensive microprocessors from MOS Technology in late 1975 made this feasible. The console was prototyped as codename Stella, by Atari subsidiary Cyan Engineering. Lacking funding to complete the project, Bushnell sold Atari to Warner Communications in 1976.

The Atari VCS launched in 1977 with nine simple, low-resolution games in 2 KB cartridges. The system's first killer app was the home conversion of Taito's arcade game Space Invaders in 1980. The VCS became widely successful, leading to the founding of Activision and other third-party game developers and to competition from console manufacturers Mattel and Coleco. By the end of its primary lifecycle in 1983–84, games for the 2600 were using more than four times the storage size of the launch games with significantly more advanced visuals and gameplay than the system was designed for, such as Activision's Pitfall!.

In 1982, the Atari 2600 was the dominant game system in North America. Amid competition from both new consoles and game developers, a number of poor decisions from Atari management affected the company and the industry as a whole. The most public was an extreme investment into licensed games for the 2600, including Pac-Man and E.T. the Extra-Terrestrial. Pac-Man became the system's biggest selling game, but the conversion's poor quality eroded consumer confidence in the console. E.T. was rushed to market for the holiday shopping season and was critically panned and a commercial failure. Both games, and a glut of third-party shovelware, were factors in ending Atari's relevance in the console market. Atari's downfall reverberated through the industry resulting in the video game crash of 1983.

Warner sold Atari's home division to former Commodore CEO Jack Tramiel in 1984. In 1986, the new Atari Corporation under Tramiel released a lower-cost version of the 2600 and the backward-compatible Atari 7800, but it was Nintendo that led the recovery of the industry with its 1985 launch of the Nintendo Entertainment System. Production of the Atari 2600 ended on January 1, 1992, with an estimated 30 million units sold across its lifetime.