Segagaga is a 2001 role-playing simulation video game developed by Hitmaker and published by Sega for the Dreamcast in Japan. Described as a "Sega simulation", the player takes control of Sega Tarō, who must help save a struggling Sega from losing to its rival DOGMA, who owns 97% of the console market. Gameplay involves battling employees and other characters throughout various Sega development studios, some being taken from older Sega game franchises. It features many tongue-in-cheek references to Sega and the video game industry, particularly Sony Computer Entertainment and its PlayStation 2 console.

Development was directed by Tez Okano, who developed the game in secret for two years before presenting it to Sega. The company misconstrued the game as a joke at first and dismissed it, but a second presentation impressed them and allowed development to continue. Okano marketed the game himself with a small budget of $200, half of which he spent on a wrestling mask to promote the game. Several characters, such as Segata Sanshiro and a Ferrari from Out Run, had to be cut due to licensing issues. Toei Animation produced the game's animated cutscenes. The game was initially exclusive to the Sega Direct online service, but its popularity eventually resulted a physical release.

Segagaga received a favorable reception from critics, being commended for its humor, gameplay, and bizarre nature, as well as its usage of various Sega franchises and for poking fun at the industry itself. One critic labeled the game as the "swan song" of the Dreamcast. It is one of the last games for the Dreamcast, having been released two days before the console's discontinuation on March 31, 2001.

Segagaga is a role-playing simulation video game, described as a "Sega simulation". Controlling the young Sega Tarō, the player is tasked with saving a struggling Sega from losing the console market to their rival DOGMA. The player must progress through various Sega development studios and fight various employees, who due to the stress and pressure brought on by tight work constraints have turned into mutants. Unlike other role-playing games, Tarō "attacks" by shouting verbal abuses and insults, such as telling them their game is terrible or they will never get a girlfriend. Enemies have a "will meter" that weakens as the player deals more insults towards them, and will win the fight once it fully drains. Failing to defeat an enemy will result in a month of development time being lost, which will become critical as the game progresses.

Once an enemy is defeated, they may become willing to ally with the player and aid them in their adventure. Should the defeated enemy accept, the player will need to quickly answer questions within a ten-second timer, such as how much the employee will make and what work conditions there are. If the player succeeds, they can place the new employee into one of four development group positions, including director, designer, planner, and programmer — development teams will increase the player's stamina and "creativity", detrimental to later sections of the game. Based on player decisions, teams can either make a small number of high-quality games or quickly produce shovelware games to hopefully generate profit. The game will end after three years of development time are completed; the ending is based on the player's performance.

A notable feature of Segagaga is its many cameos and callbacks to other Sega game franchises, alongside tongue-in-cheek parodies of the game industry itself. Tarō will come across numerous Sega characters throughout the game, including Sonic the Hedgehog, Ristar, Alex Kidd, Sir Pepper III from Clockwork Knight, Nei from Phantasy Star 2, Opa-Opa from Fantasy Zone, the Bad Brothers from Golden Axe, Panda from Baku Baku Animal, Amigo from Samba de Amigo, and the F-14 Tomcat from After Burner. Towards the end of the game, Tarō pilots a starship known as the "R-720", a nod to the R-360 arcade cabinet, into outer space that features a shoot'em up level reminiscent of Thunder Force. Tarō will fight various mechs designed after older Sega game consoles, such as the Sega Genesis and Master System. The story takes place in the year 2025, depicting Sega with having only a 3% share of the console market, the other 97% being owned by their rival DOGMA — a spoof of Sega's rival Sony Interactive Entertainment, featuring parodies of the PlayStation 2 and other Sony characters. To help save the company from total collapse, Sega establishes "Project Segagaga", led by company newcomers Sega Tarō and Yayoi Haneda in order to assist Sega in claiming 100% of the market and achieving world domination.

Segagaga was directed and designed by Tez Okano, who worked on the game in secret for two years before presenting it to the company, fearing that "anything could have happened" if the project was revealed. When it was initially shown off, Sega's management misconstrued the game as a sort of joke, and dismissed the game. When Okano presented the game again, Hitmaker president Hisao Oguchi became impressed and allowed development of the game to continue. The game was produced on a small budget. Toei Animation produced the opening and cutscenes; because of the budget, Okano was given a small discount.

Development was handled by Hitmaker, a production studio best known for titles such as Virtua Tennis and Crazy Taxi. The game was originally titled Sega Sega, later being changed to Segagaga to make the word "Sega" sound less intrusive. Early versions of the game had nearly 300 production issues, some of which caused characters to be removed from the game entirely, such as the Japanese Sega Saturn mascot Segata Sanshiro and the Ferrari from Out Run. Okano utilized a large number of Sega franchises due to their popularity and for them being freely available to use. Once the finished product was presented, Sega felt that it didn't cast a negative impression on the company and authorized its release. Toshiharu Yamanishi, who previously worked on the early Atelier series, was a composer.