Ruth Fainlight was born in New York City in 1931. She was educated in the United States and England, and has lived in England since the age of 15, mostly in London. She lived in Spain for four years in her 20s, and has spent long periods in France and Morocco.

Her first poetry collection, Cages, was published in 1966. She was Poet in Residence at Vanderbilt University, Nashville, Tennessee, in 1985 and 1990. She was Writing Tutor (for libretti) at the Performing Arts Labs, International Opera and Music Theatre Labs in the UK in 1997-99.

Her New & Collected Poems (Bloodaxe Books, 2010) covers work written over 50 years, drawing on over a dozen books as well as a whole new collection, translations and libretti. Four of those collections were originally published by Bloodaxe, including Sugar-Paper Blue (1997), which was shortlisted for the Whitbread Poetry Award. Other collections were published by Macmillan, Hutchinson and Sinclair-Stevenson.

Ruth Fainlight's collections of short stories include Daylife and Nightlife (André Deutsch, 1971) and Dr Clock's Last Case and Other Stories (Virago, 1994). As a poet, short-story writer and translator, she has contributed to many anthologies. Her own work has been translated into Portuguese, French, Spanish, Italian and Romanian, and she has herself published translations from the Portuguese of the poetry of Sophia de Mello Breyner, and from the Spanish of several Latin American poets represented in her New & Collected Poems.

She has also written four libretti: The Dancer Hotoke (1991), a chamber opera with music by Erika Fox, performed as part of the Royal Opera's 'Garden Venture' in 1991 and shortlisted for the Laurence Olivier Award for Outstanding Achievement in Opera; The European Story (based on her poem of the same title, 1993), also commissioned by the Royal Opera House; and Bedlam Britannica, which was commissioned by Channel 4 Television for the series War Cries in 1995; and The Bride in Her Grave.

Her translation (with Robert J. Littman) of The Theban Plays by Sophocles (Oedipus the King, Oedipus at Colonus and Antigone) was published in 2009 in the Johns Hopkins University Press's New Translations from Antiquity series.

She lives in London, and was married to the late Alan Sillitoe for over 50 years. She collaborated with him on an adaptation of Lope de Vega's play Fuenteovejuna, commissioned by the National Theatre and published as All Citizens Are Soldiers.

She has received the Hawthorden Award and the Cholmondeley Award for Poetry, and is a Fellow of the Royal Society of Literature.

An audio CD, Ruth Fainlight Reading from her Poems, was issued by The Poetry Archive in 2008.