Ulla Ryum was born in Frederiksberg in Copenhagen, had a Catholic upbringing, and trained to work in the hotel industry and as a sandwich maker.
1962 saw the publication of her debut novel Spejl, which deals with the themes of unintegrated personality, alienation, and awareness of death, thus fitting in with emerging Danish modernism. Numerous prose works, a number of dramatic works, children's productions, and ballets ensued. Among the best known of her works are the novels Natsangersken, 1963, and Latterfuglen, 1965, and her stories Jakelnatten, 1967, in which Ulla Ryum experiments with strong references to myths and tales. In later collections of stories, Tusindskove, 1969, and Noter om idag og igår, 1971, she strives to find a more simple form of expression.
She was active in the protest movement against the Vietnam War, in the new grassroots movements, and the gender debate, which is reflected in a number of plays written for the Royal Danish Theatre, radio theatre, and the playhouse Folketeatret in Copenhagen depicting the destruction and victims of modern warfare, the threat of environmental disaster, and the power of resistance and love. Seks skuespil, a collection of scripts, was published in 1990.
In the period from 1964 to 1966, she was a teacher at the art folk high school Kunsthøjskolen in Holbæk and from 1975 to 1978 chair of Danmarks Demokratiske Kvindeforbund (Danish democratic women's league). She has worked as a director at the Royal Danish Theatre, radio theatre, and television theatre. In 1987 she published a series of articles and essays on forms of expression used by women, Kvindesprog – udtryk og det sete; in 1993, she completed her thesis Dramaets fiktive talehandlinger and received her PhD.