The Kraith stories are a set of inter-connected works of Star Trek fan fiction. The earliest were written by Jacqueline Lichtenberg (also creator of the Sime~Gen Universe books) beginning in 1969 and continuing through the first few years after the cancellation of the original TV series. As such, Kraith represents some of the earliest Star Trek fan fiction. The stories are named after the kraith, a goblet or chalice used in the performance of certain Vulcan rituals, featuring prominently in several of the stories in the sequence.
The first few stories were published in the T Negative fanzine, under the editorship of Ruth Berman, beginning with Spock's Affirmation in T-Negative 8. As interest grew, later stories were published in a wider range of outlets, and other authors began to make contributions to the sequence of stories. Over fifty amateur and professional authors have now contributed to Kraith.
The universe portrayed in Kraith is not canon Star Trek, but its emphasis on stories with sociological, psychological and emotional plotlines had, and continues to have, a substantial impact on Star Trek fan fiction. A high proportion of early contributors to the Kraith storyline were women, and this has continued to be reflected in the high proportion of female fan writers.
The story of Kraith is ostensibly "Spock finds a wife," but this is only a trivial incident compared to the thoughts and ideas presented in the series. The central premise concerns the fact that in the original Star Trek, humans were portrayed as the dominant race throughout the galaxy. In many episodes, Kirk was shown as imposing not just human values, but his particular version of human (that is to say, white, male and 20th-century American) values, on a number of alien cultures, supposedly for their own good or to save them from being conquered by the Klingons. Lichtenberg presents this imposition as reflecting the overall attitude of the Earth-dominated Federation toward unaffiliated and member worlds. How would alien races respond to such treatment? How would they feel about the aggressive capitalism practiced by Earth companies, the influx of human residents on their worlds, the influence of human cultural values, and the eventual threat to their cultures as a result? Even if they were happy to have their world belong to the Federation, what would happen when their young people tried to join Starfleet, only to find that starships like the Enterprise are designed with only human comfort in mind? 
Vulcan, with its monoculture derived from the Reforms of Surak, has been deeply affected by contact with other races. Many Vulcans feel the changes are not for the better, and a major plot arc in Kraith concerns a proposal that Vulcan secede from the Federation. It is officially voted down, but there are still many who agree with the idea. Lichtenberg's goal was to show that the Vulcan culture we saw on the show was not perfect, and that contact with other civilizations would help post-Reform culture evolve from its present, static form, to "what it ought to become". The friendship between Kirk, Spock, and McCoy became a microcosm reflecting these changes. 
Lichtenberg tackled these issues in depth and with complexity. She is on record as having believed at the time that most people were incapable of accepting the ideas she proposes, because they were far too radical or ahead of their time.  Today, readers might see them as postmodern, or at least as bearing the seeds of critical race theory and critical cultural studies, or perhaps in terms of accommodation.
Kraith took a different turn with the input of Sondra Marshak as Lichtenberg's chief collaborator. One of Lichtenberg's plot arcs concerned the idea that James T. Kirk, having been in contact with a number of telepathic alien species, had begun to be telepathic himself. To learn control and proper use of his new abilities he came to Vulcan to attend a psychic school. For this and other reasons, some politically complex, he was adopted by Sarek and educated in the Vulcan way of life. This education had occasionally involved a "Warder-Liege compact" between Kirk and Spock, in which Kirk accepted Spock as his mentor and obeyed his commands (or vice versa, as in the Kraith novel Federation Centennial). Marshak evidently saw further plot possibilities in the Warder-Liege, and revived and expanded on its implications. Later Kraith stories are rife with BDSM undertones, and in one entry, Joan Winston's "The Maze" (published in Metamorphosis 2), Spock is depicted as giving Kirk a sound spanking for disobeying an order (in favor of saving Spock's life) while under Warder-Liege restrictions.
Although the classic Kraith stories are not slash fiction, some commentators have seen Kraith as a precursor to some forms of slash: hurt/comfort themes, and themes of emotional and mental closeness, as well as the BDSM implications later in the series, are clearly closely related to themes found in many slash stories.
Lichtenberg is perhaps best known for her Sime – Gen Universe series, which she began writing in 1969. She also worked on Marion Zimmer Bradley's Darkover series. As of 2010, she is at work on a series of original vampire slash novels with Jean Lorrah.
- Spock's Affirmation, entire text online at simegen.com, page found 2010-05-09.
- Bacon-Smith, Camille, "Spock Among the Women". New York Times, November 16, 1986, specifically mentions Kraith and its "story tree" collaborations among amateur writers.
- Bacon-Smith, Camille, Enterprising Women, Television Fandom and the Creation of Popular Myth (University of Pennsylvania Press, 1992). Expansion of her New York Times article. Has a more detailed look at Kraith "story-tree" collaborations, in the context of examining whether women write fiction differently from men.
- Jewett, Robert, The American Monomyth. New York: Doubleday, 1977.
- Verba, Joan-Marie, Boldly Writing, a Trekker Fan and Zine History, 1967-1987. FTL Publications, second edition, 2003.
- Reid, Sean, Between the Worlds: Readings in Contemporary Neopaganism. Canadian Scholars' Press, 2006.
- Ashley, Michael, Gateways to forever: the story of the science-fiction magazines. Liverpool University Press, 2007.
- Lichtenberg, Jacqueline, Federation Centennial, chapter 3. Page found 2010-05-02.
- Lichtenberg, "Author's Preface", Kraith Collected, p. 4.
- In the "Author's Preface" to Kraith Collected I, p. 3, she explains the necessity of "gently introducing" readers to her ideas over a multi-story series: "The concepts are radical and very strange. Not one in five hundred would be able to accept them."
- Kraith Home Read the first six volumes of Kraith Collected on line. These are the stories written by Lichtenberg and by other Kraith writers, printed in the correct order of their occurrence. The essay Understanding Kraith and the Kraith Creators' Manual are also provided.