The YuYu Hakusho manga series features a diverse cast of characters created by Yoshihiro Togashi. It follows a fourteen-year-old junior high school delinquent Yusuke Urameshi, who dies but is resurrected to become the Underworld's detective of paranormal events in the Human World. He begins his work in the Human World, but ends up traveling to the Underworld and then eventually to the Demon Plane. In each case he undertakes, Yusuke meets several new enemies and allies. Other predominant characters include Yusuke's rival delinquent Kazuma Kuwabara, the fox demon Kurama, and the sword-wielding fire demon Hiei. While several characters are humans, many are demons, and both have different supernatural abilities due to harnessing their Reiki, one's own aura or life energy.

Togashi did not give much thought to the names of the characters. He came up with them by skimming through a dictionary and combining kanji characters he found appealing. The author said the name Yusuke Urameshi is "practically a joke." Viz Media explained that the "Yu" is written with the kanji for "ghost", and "Urameshiii..." is a phrase typically said by wailing ghosts.

Togashi came up with Kazuma Kuwabara's name by combining the names of two professional baseball players (Masumi Kuwata and Kazuhiro Kiyohara). Viz Media said that it is also a pun on "Kuwabara kuwabara", a phrase uttered by superstitious people when they are scared. Mari Kitayama, a lead character designer for the anime adaptation of Yu Yu Hakusho, stated that she considers Kuwabara to be the most difficult character to design.

Kurama and Hiei's names came to Togashi on the spur of the moment. When the two were introduced, the author had early plans to make Kurama a main character but was uncertain about Hiei. Togashi based Hiei's design off of the character Skunky from the manga series Patalliro! by Mineo Maya. Kitayama finds Kurama to be the easiest of the main characters to design due to his well-proportioned features and considers Hiei to be her favorite.

The names of Yusuke's school, Sarayashiki, and the rival Kasanegafuchi Junior High are both named after haunted mansions in famous ghost stories; Banchō Sarayashiki and Kaidan Kasanegafuchi.

The names of the characters Roto and Rinku are taken from video game characters of the same names, the former from Dragon Quest and the latter from The Legend of Zelda.

Togashi's inspiration for the character Mukuro was Kushana of Torumekia from Nausicaä of the Valley of the Wind.

After receiving many letters both praising and criticizing the voice actors, Togashi clarified that he had no involvement in the anime adaptation.