Monthly Ikki (Japanese: 月刊IKKI, Hepburn: Gekkan Ikki) was a monthly seinen manga magazine published by Shogakukan. It tended to specialize in underground or alternative manga, but it had its share of major hits as well. The magazine started in 2000 as a spin-off to Shogakukan's Weekly Big Comic Spirits, titled Spirits Zōkan Ikki, published on a bimonthly basis, and became a standalone monthly magazine in 2003. In 2009, Viz Media launched an online English version of Monthly Ikki, named SigIkki, which serialized selected titles from the magazine. Ikki ceased publication after an almost 14-year-run in 2014, and was replaced by Hibana [ja], which ran from 2015 to 2017, before ceasing its publication as well.

Editor Hideki Egami [ja], who spent 18 years in the editorial department of Shogakukan's Weekly Big Comic Spirits, observed the increasing sophistication of manga and believed some manga artists were better suited to monthly rather than weekly serialization. He noted that weekly series often required large teams of assistants and a fast-paced workflow, whereas monthly publication allowed creators like Taiyō Matsumoto (known for Tekkonkinkreet) to work more independently and deliberately. Egami credited Matsumoto with persuading him to develop a new magazine.

Egami conceived the magazine as a monthly spin-off of Weekly Big Comic Spirits. Naming the publication proved difficult due to trademark issues. After a rejected proposal to solicit names from readers, Egami and magazine designer Shin Sobue [ja] chose "Ikki" for its positive connotations, pleasing sound, and available copyright. The magazine launched as Spirits Zōkan Ikki (スピリッツ増刊IKKI, Supirittsu Zōkan Ikki), releasing 13 bimonthly issues from November 30, 2000, to December 25, 2002. It became a standalone monthly publication with its April 2003 issue, released February 25.

In 2009, Viz Media launched SigIkki, an English-language online version of Monthly Ikki. Egami acknowledged the defunct American magazine Pulp as a precursor that helped pave the way for Ikki's acceptance in the United States. With the magazine's original pages already digitized, Egami saw translation as an opportunity to reach a broader audience. The digital files, which separated text and art into layers, facilitated localization. Former Viz Media editorial manager Leyla Aker noted the project was internally nicknamed "Pulp 2.0" and shared the Viz Signature imprint's goal of publishing creatively excellent and diverse content. Monthly Ikki was also Shogakukan's first manga magazine to publish digitally. The SigIkki website serialized titles online, with popular series later receiving print publication, and featured interviews with creators and editors. In January 2013, the magazine's official site, Ikki Paradise, launched Web Ikipara Comic (WEBイキパラCOMIC), a free web manga corner serializing original online content.

After nearly 14 years, the September 2014 issue (released July 25) announced that Monthly Ikki would cease publication with the November issue (released September 25). Some series concluded in the final issue, while others transferred to different magazines. It was replaced by Hibana [ja], which launched in March 2015. Hibana itself ceased publication after two years, with its final issue released in August 2017.

Well, not too long ago I was watched Shine a Light, and that reminded me of this quote of Keith's that I read about fifteen years ago. A reporter asked him something like, "What does it take to be like you?" Keith being Keith—that is, a much better talker than Mick—answered, "Stop trying to be like me." In other words, to be like Keith, you can't be like Keith. I want people out there to read IKKI in order to get inspired to create something brand new, not to become an IKKI look-alike. Be ready to make an entire genre yourself. Keep on digging underground to a whole new level even if you don't know what you'll find there.

Monthly Ikki was regarded as an underground publication and was frequently compared to American and European alternative comics for its content. The magazine prioritized authorial creativity over audience expectations. As Egami explained, his boss contrasted its approach with that of Weekly Big Comic Spirits: "for IKKI, you have to see the spring that is the origin of the river, meaning you have to see the creator and work with the creator; that it's important to understand the artists' point of view." This philosophy led the magazine to advertise itself as a "comics magazine" rather than a "manga magazine" to distinguish its unconventional content.

Its slogan, "[w]e are still at the dawn of the manga era," reflected an optimistic view of the medium's potential. Egami elaborated that this meant "if you assume that the history of manga will continue for 200 years or longer, we are still at the very beginning", suggesting ample room for innovation and growth beyond the perceived saturation of the market. He further expressed a belief in the future emergence of creators who could stand alongside Osamu Tezuka.