Quin was born in Brighton in March 1936, in a family on the fringes of the working-class and lower-middle class; her father left them and she was raised by her mother alone. She was educated at a Roman Catholic school, the Convent of the Blessed Sacrament in Brighton, until the age of 17. She trained as a shorthand typist and worked in a solicitor's office, then at a publishing company when she moved to Soho and began writing novels.
Quin is also said to have ghost-written the thesis of her then-partner, pop artist Billy Apple.
She suffered mental health problems, suffering a breakdown whilst working in a hotel in Cornwall, and later receiving electro-shock treatment. She committed suicide during the first Bank Holiday weekend of August 1973, drowning herself off Brighton's Palace Pier, weeks before the death of her contemporary B. S. Johnson. A man called Albert Fox witnessed a woman walking into the sea and contacted the police; the next day, a yachtsman found a body near Shoreham Harbour. An appeal was launched in Brighton & Hove's local newspaper, The Argus, and the woman was identified as Quin. The coroner recorded an open verdict.
Quin is associated with a loosely constituted circle of 'experimental' authors in Sixties Britain, headed by B. S. Johnson and including Stefan Themerson, Rayner Heppenstall, Alan Burns and Eva Figes, influenced by Samuel Beckett and recent French fiction (Marguerite Duras, Alain Robbe-Grillet). They stood in opposition to the dominant tendency for social realism, manifest from John Osborne and John Wain to Karl Miller's Writing in England Today (Penguin, 1968).
Her first novel, Berg, was published by John Calder in 1964. Influenced by Virginia Woolf, Anna Kavan and other female British modernists, as well as the French nouveau roman. Its opening line, 'A man called Berg, who changed his name to Greb, came to a seaside town intending to kill his father...' set the tone for a dark, psychological farce set in an unnamed seaside town that clearly resembles Brighton, which became the most critically acclaimed of her four novels.
Berg was followed by Three (1966), Passages (1969) and Tripticks (1972), illustrated by her lover Carol Annand, in which Quin continued her formal experimentation, although without making the same critical impact as she had with her debut.
Her work has somewhat fallen into obscurity since her death, such that Lee Rourke could say in 2007: "Who cares about Ann Quin? I do, for one, but why does no one else seem to remember this writer from the front rank of Britain's literary avant-garde?" However, there has been a complete reprint of her works by Dalkey Archive Press as well as a critical biography by Robert Buckeye, with a collection of rare and previously unpublished stories and fragments, The Unmapped Country, due from And Other Stories in 2018. Contemporary non-mainstream authors such as Stewart Home, Tom McCarthy, Chloe Aridjis, Deborah Levy, Juliet Jacques, Joanna Walsh and Rourke have cited her work as influential.