Doris Amelia Blackburn (née Hordern) (18 September 1889 – 12 December 1970) was an Australian political activist and member of parliament.
Born in Hawthorn, Melbourne, Victoria to Lebbeus Hordern, estate agent, and his wife Louisa Dewson (née Smith), Doris Hordern became involved in women's rights and peace issues from a young age and served as the campaign secretary of Vida Goldstein, the first woman to stand for election to federal parliament in Australia. She married Maurice Blackburn, a fellow firebrand socialist, in Melbourne on 10 December 1914 and spent their honeymoon organising anti-war and anti-conscription campaigns. While her husband served at different times as an Australian Labor Party (ALP) member of the Victorian and Federal parliaments, Blackburn continued to work on social issues, a few of which brought her into conflict with the Labor Party (of which she too was a member) and following Maurice's expulsion from the party in 1937, she resigned from the ALP. Her husband continued to sit in parliament as an independent but lost his seat at the 1943 federal election to the official Labor candidate, and passed away the following year.
Upset at Labor's treatment of her husband, Doris stood as an Independent Labour candidate for Maurice's old seat of Bourke at the 1946 election, and by winning it she became only the second woman to be elected to the Australian House of Representatives.
In parliament Blackburn, who shared the cross benches with fellow former Labor member Jack Lang, championed similar issues to those of her late husband, gaining nationwide notoriety in 1947 as the only MP to vote against the Atomic Energy Bill. She served as the national President of the Council for Civil Liberties. Following an electoral redistribution, her seat of Bourke was abolished, and at the 1949 election she contested the newly established seat of Wills. In a contest with both the Labor and Liberal parties she came third with 20 percent. Standing in Wills again at the 1951 election she additionally came third with 17 percent of the vote. Both times the seat was convincingly won by Labor.
Blackburn subsequently remained active in social issues, serving as president of the Women's International League for Peace and Freedom. Realising the problems faced by Aborigines, following a visit to the Woomera Rocket Range, she co-founded, with Douglas Nicholls, the Aborigines Advancement League and the Federal Council for Aboriginal Advancement.