Sound Horizon is a Japanese musical group and creative entity, best understood as an original creator behind a series of manga and anime adaptations. The group was founded in 2001 by the composer, lyricist, and musician Revo, who remains its sole permanent member and creative leader. While Sound Horizon is primarily a musical project that describes itself as a fantasy band, its work forms the source material for a number of manga series. The group first began as a dōjin (self-published) music circle, releasing story-driven concept albums at events like Comic Market, before making its major label debut in 2004 with the album Elysion ~Rakuen e no Zensōkyoku~.

Sound Horizon is credited as the original creator for several manga adaptations based on its story albums. These include the manga Elysion: Futatsu no Rakuen o Mawaru Monogatari, based on the group's fourth story album Elysion ~Rakuen Gensō Monogatari Kumikyoku~, and the manga Roman, derived from the fifth story album Roman. Other manga adaptations for which Sound Horizon is listed as the original creator include Moira and Shinyaku Märchen, based on the sixth and seventh story albums, respectively. These manga series serve as visual and narrative expansions of the complex stories originally presented through Sound Horizon's music. The group's history of manga adaptations is extensive, with nearly all of its major albums being adapted into manga form by various artists.

Beyond its role as a manga originator, Sound Horizon has significant ties to the anime industry through a related alias. In 2012, Revo launched a separate project named Linked Horizon, which is used specifically for commercial collaborations with other media, including video games and anime. Under the Linked Horizon name, the group has achieved mainstream international recognition for producing several iconic theme songs for the globally popular anime series Attack on Titan, including the opening themes Guren no Yumiya and Jiyū no Tsubasa, as well as ending themes for later seasons. Revo has also composed music for other anime, such as the opening theme for Sailor Moon Crystal.

The artistic identity of Sound Horizon is defined by its creation of what it calls story music or fantasy band music. Their work is characterized by symphonic rock and classical suite-like compositions that tell a single, overarching narrative across an entire album. These stories frequently draw from European history, classic fairy tales, mythology, and original fantasy worlds, often exploring dark, tragic, or gothic themes where death and fate are common motifs. The music incorporates a wide array of vocalists, narrators, and sound effects to create a theatrical, almost cinematic listening experience, which is further enhanced by elaborate live concerts that resemble stage musicals. The group has a dedicated fan community that refers to itself as the Sound Horizon Kingdom, with fans known as Laurant and Revo as the King.

Sound Horizon holds a unique position in the Japanese entertainment industry as a bridge between the independent dōjin music scene and mainstream commercial success. Beginning as a small internet-based project, the group grew to achieve gold record certification and top rankings on the Oricon charts, demonstrating that a concept-driven, narrative-focused musical project could find a large audience. Its influence is seen in its pioneering of the story music genre, its success in expanding its original stories into other media like manga, and its ability to transition into a highly sought-after commercial entity under the Linked Horizon alias for major anime franchises.