Marion Louisa Piddington (1869–1950) was an Australian publicist active in the promotion of eugenics and sex education. The wife of judge and politician Albert Bathurst Piddington, and related to Australian literary and political figures, she promoted ideas of racial hygiene and single mothers through association with several organisations and progressive movements.
Piddington was most well known for her advocacy of contraception, 'celibate motherhood', racialist theory and social legislation in Australia during the interwar period of the nineteen twenties and thirties, works that were neglected until the nineteen eighties; Peddingtons first biographer concludes, "She defied modern categories such as 'puritan' or 'libertarian', being in some curious measure both."