Chex Quest is an ostensibly non-violent first-person shooter video game created in 1996 and released in 1997 by Digital Café, originally intended as a Chex cereal promotion aimed at children aged 6–9 and up. It is a total conversion of the more explicitly violent video game Doom (specifically The Ultimate Doom version of the game). Chex Quest won both a Golden EFFIE Award for Advertising Effectiveness and Golden Reggie Award for Promotional Achievement in 1998, and it is known today for having been the first video game ever to be included in cereal boxes as a prize. The game's cult following has been described by the press as being composed of unusually devoted fans of an advertising vehicle from a bygone age.

In 2019, General Mills rereleased Chex Quest and its previously unofficial 2008 sequel, and presented a mini-documentary on YouTube.

Originally based on the Doom engine, the gameplay present in Chex Quest is substantially identical to its predecessor. The game is played in a first person perspective with the player character navigating through quasi-3D environments while enemies attempt to attack and immobilize him. Along the way, various cereal-themed power-ups, weapons, and ammunition can be found that can boost the player character's health and make him better able to counterattack or flee his enemies. When the final boss is defeated in the last level, the game is won.

A few notable differences from Doom are evident, however, regarding enemy profiles (specifically the loss of long-range attacks in low-level enemies and the loss of movement in high-level enemies) and the number of levels in each world (restricted to 5 levels in Chex Quest).

Set on a distant planet named Bazoik, the game follows the Chex Warrior, a soldier clad in a Chex-shaped suit of armor, as he foils the invasion of the planet by the 'Flemoids': a species of slimy, green invertebrates, who have infested the planet and captured many helpless colonists, whom the Chex Warrior must save. His main weapons are devices called "zorchers", which teleports his enemies to their home dimension. The game starts at the landing pad of the research center on Bazoik; other levels include the laboratory, the arboretum, and finally, the caverns of Bazoik, where the Flemoids have established their colony. Their principal weapon is the use of mucus as a projectile.

Produced with a small team of developers on a budget of around $500,000, Chex Quest was created by the WatersMolitor promotion agency, which had been hired by Ralston Foods to promote the Chex cereal brand. The original game concept was created by Dean Hyers and Mike Koenigs as a non-violent CD-ROM computer game to be released with 5.7 million boxes of Rice Chex, Wheat Chex, and Corn Chex cereals in order to cast Chex as a cereal that was exciting and fun for children while appealing to modern sensibilities by targeting home PC owners. The game would be a high-quality program whose normal retail value would be between $30 and $35. However, it would be offered to consumers for free with no increase to the cost of the cereal box.

The development of Chex Quest differed from traditional video game development in that the basic game engine had already been created and the bulk of the creation process consisted of aesthetic changes made to the music and artwork from The Ultimate Doom. For budgetary reasons, Id Software was contacted and an inexpensive license was obtained for the Doom engine which was considered obsolete in light of Id's then-recent release of Quake. Chex Quest was the first foray into professional game development for lead artist Charles Jacobi and programmer Scott Holman, though both had previously modded Doom levels in the past. In an interview with PC Gamer magazine in 2009, Jacobi stated that the biggest reason for the lasting success of Chex Quest has been that it is still essentially a disguised version of Doom with basically unaltered game dynamics. Indeed, the game has been recognized for having a sense of humor about its identity and origins.

Humorous aspects of the conversion take the form of ironic in-jokes related to Doom resulting from the more or less exact "translation" of previous non-essential Doom decorations into their non-essential Chex Quest equivalents. Thus the bloodied bodies and the twitching torsos from Doom become the goo-covered cereal pieces and the cereal victims twitching to extract themselves from goo in Chex Quest. Likewise, according to the plot the "health" meter represents the Chex Warrior's ability to move, with 0% representing being completely covered in slime and unable to move. The picture of the Chex Warrior in the status bar display becomes progressively more coated in slime, as opposed to bleeding as does Doomguy's face in the Doom status bar. Because time was limited, pre-existing tools popular with the Doom fan community (such as the level creation tool Doombuilder) were utilized in level design, and sound effects such as the distinctive vocalization of the Flemoids were created by creative director Dean Hyers and audio designer Andrew Benson playing around in a sound booth.