Iain Sinclair was born on 11 June 1943 in Cardiff. His education includes studies at Trinity College, Dublin, where he edited Icarus, the Courtauld Institute of Art (University of London), and the London School of Film Technique (now the London Film School).

His early work was mostly poetry, much of it published by his own small press, Albion Village Press. He was (and remains) closely connected with the British avant-garde poetry scene of the 1960s and 1970s; later on, taking over from John Muckle, Sinclair edited the Paladin Poetry Series and, in 1996, the Picador anthology Conductors of Chaos.

His early books Lud Heat (1975) and Suicide Bridge (1979) were a mixture of essay, fiction and poetry; they were followed by White Chappell, Scarlet Tracings (1987), a novel juxtaposing the tale of a disreputable band of bookdealers on the hunt for a priceless copy of Arthur Conan Doyle's A Study in Scarlet and the Jack the Ripper murders (here attributed to the physician William Gull).

Sinclair was for some time perhaps best known for the novel Downriver (1991), which won the James Tait Black Memorial Prize and the 1992 Encore Award.Much of Sinclair's recent work consists of an ambitious and elaborate literary recuperation of the so-called occultist psychogeography of London. Other psychogeographers who have worked on similar material include Will Self, Stewart Home and the London Psychogeographical Association. In 2008 he wrote the introduction to Wide Boys Never Work, the London Books reissue of Robert Westerby's classic London low-life novel. Hackney, That Rose-Red Empire: A Confidential Report followed in 2009.

Iain Sinclair lives in Haggerston, in the London Borough of Hackney, and has a flat in Hastings, East Sussex.