Ann Katharine Mitchell ( Williamson; 19 November 1922 – 11 May 2020) was a British cryptanalyst and psychologist. She was born in Oxford.
Mitchell worked on decrypting messages encoded in the German Enigma cypher at Bletchley Park during the Second World War. After the war, she became a marriage guidance counsellor, then studied for a Master of Philosophy at the University of Edinburgh.
She worked at the university's Department of Social Administration and wrote several academic books about the psychological effects of divorce on children including Someone to Turn to: Experiences of Help Before Divorce (1981) and Children in the Middle: Living Through Divorce (1985).
Mitchell died on 11 May 2020, aged 97, in Edinburgh of COVID-19.