Olwen Anne Elisabeth Rasa (1940 – 15 November 2020) was a British ethologist, known for her long-duration study of the social behaviour of the dwarf mongoose in Kenya. She had studied aggression among coral reef fish under the pioneering ethologist Konrad Lorenz. Her fieldwork in Kenya's Taru Desert led to a book, Mongoose Watch: A Family Observed, and to a popular German television series, Expedition ins Tierreich. She later studied social behaviour in the yellow mongoose and the sub-social tenebrionid beetle Parastizopus armaticeps.