Written by Hiroya Oku, the manga chapters have been published in the Japanese magazine Weekly Young Jump since 2000 and is finished on June 20, 2013; the individual chapters of the series were being released approximately every fifteen days. Gantz is divided into three main story arcs referred to as "phases". After the completion of Phase 1, the author put the series on hiatus for a short time to work on Phase 2, which is also known as "Katastrophe". Phase 1 consists of the first 237 chapters. On November 22, 2006, the first chapter of Phase 2, chapter 238, was released. Phase 2 consists of chapters 238 through 303. The third and final phase began on October 1, 2009, after a brief hiatus. As of June 20, 2013, the main manga series is finished at 383 chapters long (not counting specials and spin-offs). The individual chapters are collected by Shueisha in tankōbon format; the first volume was released on December 11, 2000. Currently, 37 volumes have been released by Shueisha.
Publishing company Dark Horse Comics acquired the licensing rights for the release of English translations of Gantz on July 1, 2007, during the Anime Expo. The first English volume was released on June 25, 2008. While the first three are being published quarterly, the following volumes will be released on a bimonthly basis. The series is published by Glénat in Spain and by Planet Manga in Germany, Italy and Brazil. It is published by Tonkam in France, by Editorial Vid in Mexico and by Editorial Ivrea in Argentina.
A spin-off, titled GANTZ:G, was serialized in Shueisha's Miracle Jump magazine from November 2015 to March 2017.  The manga was written by Oku and illustrated by Keita Iizuka. Dark Horse have also licensed the spin-off.
Gantz/Osaka has been published in Japan (showing the stories of the Gantz Osaka team), while Gantz/Nishi has started publication (showing the life of Nishi), and Gantz no Moto has Hiroya Oku telling the story on how he got into the manga business and what films influenced him.
An anime adaptation, produced by Gonzo and directed by Ichiro Itano, aired in Japan on Fuji Television and AT-X. The Gantz anime is divided into two seasons: "The First Stage" and "The Second Stage", which is a direct continuation of the first season. The First Stage aired in Japan with several scenes censored due to inappropriate content such as violence or nudity. However, the DVDs from the series contained the scenes uncensored. The Second Stage aired on Japanese network AT-X on August 26, 2004. There are a total of 12 Japanese DVDs, released from August 28, 2004 to June 29, 2005. Additionally, the DVDs were compiled into box sets.
ADV Films announced and licensed the series for release in the United States. The series was released in uncut form, retaining the violence and nudity previously censored in Japan for broadcast. Ten DVDs were released by ADV Films from February 8, 2005 to January 17, 2006. They also compiled the series in two DVD box sets in 2006 and in a Perfect Score Collection packaged with a bag in the form of Gantz.
On June 25, 2010, anime distributor Funimation Entertainment announced on their online FuniCon 4.0 panel, that they have acquired the rights to the series, along with 3 other former ADV titles after ADV's collapse in 2009.
The anime follows the plot of the manga up to the end of the temple mission. The last five episodes then branch off into an original story not present in the manga.
Gantz: O, a 3D CGI animated film based on the series, was released in 2016.
On March 17, 2005, Konami published a game for the PlayStation 2 in Japan named simply as Gantz: The Game. It features the characters and plot up to the Chibi Alien mission. The game mixes third-person shooter and role-playing game (RPG) elements together. The game also includes extras including Free Play mode, a Mini Mode, Magazine Browser mode, Gantz Rankings, a special preview movie and the scenario completion statistic. The game was never released overseas.
Gantz/Burst and Gantz MobileMission are cellphone games.
In July 2009, Weekly Young Jump, the seinen manga magazine, began publishing a novel from the series named Gantz/Minus. It is written by Masatoshi Kusakabe and illustrated by Yusuke Kozaki. The stories take place before the start of the manga, with the focus being on the characters Shion Izumi and Joichiro Nishi, who participate in Gantz's missions. On the cover of each Gantz/Minus issue, it describes itself as a "hyper solid action novel".
Gantz/EXA is the second Gantz novel published. It was first serialized in Jump magazine, then printed as a complete collection in January 2011.
Live action films
On November 24, 2009, it was announced that two live-action Gantz films were in production. The films star Kazunari Ninomiya and Kenichi Matsuyama in the roles of Kurono and Kato respectively, and were directed by Shinsuke Sato. The films were released in January and April 2011.
The first film, titled simply as Gantz, was released in Japan on January 29, 2011. A special North American screening took place on January 20, 2011, during which the film was simulcast in theaters across 46 states. At the end of this special Los Angeles showing, which took place at the Mann's Chinese 6 theatre, there was a discussion and live interview with both the male leads, as well as a teaser trailer for the second installment, Gantz: Perfect Answer, which is released in Japan on April 23, 2011. Gantz and Gantz 2: Perfect Answer were screened in San Diego, California as part of Comic-Con International at the Gaslamp 15 Theater on July 22 & 23.
A companion book titled Gantz/Manual was published by Shueisha on December 17, 2004. The book features episode summaries, character overviews, and additional background details on the Gantz universe. A revised edition, Gantz/Manual Remix, was published in 2011 as a supplement for Gantz manga and live action movie featuring story act summaries, manga story arc summaries, character overviews, and additional background details on the Gantz universe.