Ai no Kusabi (間の楔, lit. "The Space Between") is a Japanese novel written by Rieko Yoshihara. Originally serialized in the yaoi magazine Shōsetsu June between December 1986 and October 1987, the story was collected into a hardbound novel that was released in Japan in 1990, and eventually expanded on and released in 6 paperback volumes.

This futuristic tale is set in a world ruled by a super computer Jupiter, where its cyborg creations, the Elites, who are assigned various social roles based on their hair color, rule over the human populace. Iason Mink, a high-class "Blondy" elite from the capital Tanagura, runs into Riki, a "Mongrel" from the slums, and makes him his "Pet". This decision was seen as taboo in Tanagura where Pets are a status symbol and are expected to be well-bred, and was also unacceptable to Riki who had his freedom taken away from him. As Riki learns of the dangers Iason faces by keeping him, he finds himself developing feelings for his master. While focusing on the relationship between Iason and Riki, Ai no Kusabi also explores issues of caste systems and social exclusion, as well as the implications of Artificial Intelligence ruling over a human society.

The novel was partially adapted into a two-episode original video animation (OVA) by Anime International Company (AIC), with the first episode released in August 1992 and the second in May 1994. In November 1993, an audio drama entitled Dark Erogenous was released focusing on a time period left unexplored in the original novels. A new twelve-episode OVA adaptation, also from AIC, was scheduled to begin releasing in Japan in the spring of 2010, but was cancelled for financial reasons. The project was picked up again and was released on January 18, 2012. However, the series was once again discontinued after four episodes.

The novel is licensed for an English language release in North America by Digital Manga Publishing, which published the novel over an eight-volume series.