Kathleen Ollerenshaw, née Timpson, was born in Withington, a suburb of Manchester, England. She attended Lady Barn House School, where her fascination with mathematics began, St. Leonards School, and Sixth Form College at St. Andrews, Scotland. She read mathematics at Oxford University and earned a doctoral degree in 1945. While still an undergraduate, she became engaged to Col. Robert Ollerenshaw, later a distinguished military surgeon, and married him in 1939; the couple had two children. After World War II, Dr. Ollerenshaw was a part-time lecturer in the mathematics department at Manchester University and worked on her own mathematical research. She also became active in Conservative Party politics, serving as a councillor for Rusholme from 1956 to 1981, and winning election as Lord Mayor of Manchester in 1975. She also served as an advisor on education to Prime Minister Margaret Thatcher's government in the 1980s.
She published at least 26 scholarly papers on mathematics. Her autobiography, To Talk of Many Things, appeared in 2004.