M. John Harrison in the context of Nova Swing

The New Wave was a science fiction movement of the 1960s and 1970s, characterized by a great degree of experimentation with the form and content of stories, often influenced by the styles of non-science fiction literature, and an emphasis on the psychological and social sciences as opposed to the physical sciences. New Wave authors often considered themselves as part of the modernist tradition of fiction, and the New Wave was conceived as a deliberate change from the traditions of the science fiction characteristic of pulp magazines, which many of the writers involved considered irrelevant or unambitious.

The most prominent source of New Wave science fiction was the British magazine New Worlds, edited by Michael Moorcock, who became editor during 1964. In the United States, Judith Merril's anthologies and Harlan Ellison's 1967 anthology Dangerous Visions are often considered as the best early representations of the movement. Worldwide, Ursula K. Le Guin, Stanisław Lem, J. G. Ballard, Samuel R. Delany, Roger Zelazny, Joanna Russ, James Tiptree Jr. (a pseudonym of Alice Bradley Sheldon), Thomas M. Disch and Brian Aldiss were also major writers associated with the movement. Moorcock wanted writers to borrow from the genre's techniques but encouraged writers to develop their own styles. Apart from Moorcock and Ballard, authors included Hilary Bailey, Barrington Bayley, M. John Harrison, Pamela Zoline, Rachel Pollack and Christopher Priest.

The new weird is a literary genre that emerged in the 1990s through early 2000s with characteristics of weird fiction and other speculative fiction subgenres. M. John Harrison is credited with creating the term "New Weird" in the introduction to The Tain in 2002. The writers involved are mostly novelists who are considered to be part of the horror or speculative fiction genres but who often cross genre boundaries. Notable authors include K. J. Bishop, Paul Di Filippo, M. John Harrison, Jeffrey Ford, Storm Constantine, China Miéville, Alastair Reynolds, Justina Robson, Steph Swainston, Mary Gentle, Alistair Rennie, Michael Cisco, Jeff VanderMeer and Conrad Williams. The movement was further defined and cataloged in 2008 with the publication of The New Weird, an anthology edited by Ann and Jeff VanderMeer that compiled seminal stories and essays from the genre's proponents.