Alastair Preston Reynolds (born in 1966 in Barry, Wales) is a Welsh science fiction author. He specialises in dark hard science fiction and space opera. He spent his early years in Cornwall, moved back to Wales before going to Newcastle, where he read Physics and Astronomy. Afterwards, he earned a PhD from St Andrews, Scotland. In 1991, he moved to Noordwijk in the Netherlands where he met his wife Josette (who is from France). There, he worked for the European Space Research and Technology Centre, part of the European Space Agency, until 2004 when he left to pursue writing full time. He returned to Wales in 2008 and lives near Cardiff.

Alastair Reynolds wrote his first four published science fiction short stories while still a graduate student, in 1989-1991; they appeared in 1990-1992. In 1991 Reynolds graduated and moved from Scotland to the Netherlands to work at ESA. He then started spending much of his writing time on a first novel, which eventually turned into Revelation Space, while the few short stories he submitted from 1991-1995 were rejected. This ended in 1995 when his story "Byrd Land Six" was published, which he says marked the beginning of a more serious phase of writing. As of 2008 he has published over thirty shorter works and eight novels. His works are hard science fiction veiled behind space opera and noir toned stories, and reflect his professional expertise with physics and astronomy, included by extrapolating future technologies in terms that are consistent with current science. Alastair Reynolds has said he prefers to keep the science in his books to what he personally believes will be possible, and he does not believe faster-than-light travel will ever be possible, but that he adopts science he believes will be impossible when it is necessary for the story. Most of Reynolds's novels contain multiple storylines that originally appear to be completely unrelated, but merge later in the story. Five of his novels and several of his short stories take place within one consistent future universe, usually now called the Revelation Space universe after the first novel published in it, although it was originally developed in short stories for several years before the first novel. Although most characters appear in more than one novel, the works set within this future timeline rarely have the same protagonists twice. Often the protagonists from one work belong to a group that is regarded with suspicion or enmity by the protagonists of another work. While a great deal of science fiction reflects either very optimistic or dystopian visions of the human future, Reynolds's future worlds are notable in that human societies have not departed to either positive or negative extremes, but instead are similar to those of today in terms of moral ambiguity and a mixture of cruelty and decency, corruption and opportunity, despite their technology being dramatically advanced.

The Revelation Space series includes five novels, two novellas, and eight short stories set over a span of several centuries, spanning approximately 2200 to 40 000, although the novels are all set in a 300 year period spanning from 2427 to 2727. In this universe, extraterrestrial sentience exists but is elusive, and interstellar travel is primarily undertaken by a class of vessel called a lighthugger which only approaches the speed of light (Faster than light travel is possible, but it is so dangerous that no race uses it). Fermi's paradox is explained as resulting from the activities of an inorganic alien race referred to by its victims as the Inhibitors, which exterminates sentient races if they proceed above a certain level of technology. The first three novels of the series deal with humanity coming to the attention of the inhibitors and the resultant war between them. Century Rain takes place in a future universe independent of the Revelation Space universe and has different rules, such as faster-than-light travel being possible through a system of portals similar to wormholes. Century Rain also departs substantially from Reynolds's previous works, both in having a protagonist who is much closer to the perspective of our real world (in fact he is from a version of our past), serving as a proxy for the reader in confronting the unfamiliarity of the advanced science fiction aspects and in having a much more linear storytelling process. Reynolds's previous protagonists started out fully absorbed in the exoticisms of the future setting and his previous Revelation Space works have several interlinked story threads, not necessarily contemporaneous.

Pushing Ice is also a standalone story, with characters from much less distant in the future than in any of his other novels, set into a framework storyline that extends much further into the future of humanity than any of his previous novels. It contains an alternative interpretation of the Fermi paradox, intelligent sentient life in this universe is extremely scarce. The Prefect marked a return to the Revelation Space universe. Like Chasm City, it is a stand-alone novel within the Revelation Space universe. It is set prior to any of the other Relevation Space novels, though still 200 years after the original human settlement of the Epsilon Eridani system. It was published in the United Kingdom on 2 April 2007. On 7 June 2007, Reynolds announced that his next novel would be entitled House of Suns, and that it would be set in the same universe as his novella "Thousandth Night" from the One Million A.D. anthology. This novel was released in the UK on 17 April 2008 with an American release to follow.. He is presently working on a new novel which he has confirmed will be a standalone and is due for publication in October 2009. It is described by Reynolds in a recent interview as "it's SF, it's weird and it doesn't have spaceships". Alastair Reynolds further elaborated on the book in a recent release from StarShipSofa, saying that it would have steampunk influences.