Harry Fainlight was born in New York in 1935 to an English father and a naturalized American mother. Though the family relocated to England when he was age one, Harry, his sister, and his mother returned to America for the duration of World War II. While at Brighton and Hove Grammar School, Fainlight won a scholarship to read English literature at Pembroke College, Cambridge. He worked as an advertising executive in London before going to live in New York City. During his time there he worked on films and befriended Allen Ginsberg, Peter Orlovsky, Gregory Corso, and Lawrence Felinghetti.

After returning to live in London in the mid-1960's, Fainlight read his work at the International Poetry Incarnation at the Albert Hall in June 1965. This event brought together American Beat poets with their English peers and had seven thousand attendees. The same year, Fainlight's twelve page booklet, Sussicran ("Narcissus" backwards) was published. This is the only work Fainlight published in his lifetime. In 1967, Fainlight participated in the funeral and resurrection performance for the International Times, being carried in a coffin through the streets of London. Throughout the 1970's, Fainlight suffered mental health problems and was hospitalized several times. His relationships with family and friends, including fellow literary figures, suffered due to his behavior. By 1976, Fainlight isolated himself in a remote cottage in Wales. He passed away in a field outside his home after a struggle with bronchial pneumonia in September 1982. Ruth Fainlight edited and published a posthumous volume of Harry Fainlight's poetry called Selected Poems in 1986.