The 1975 Conservative Party leadership election was held in February 1975. The party's sitting MPs voted Margaret Thatcher as party leader on the second ballot. Incumbent leader Edward Heath stood aside after the first ballot, in which he unexpectedly finished behind Thatcher. The Conservatives were the official Opposition to the Labour government, so Thatcher also became Leader of the Opposition.

Margaret Hilda Thatcher, Baroness Thatcher, was a British stateswoman and Conservative politician who served as Prime Minister of the United Kingdom from 1979 to 1990 and Leader of the Conservative Party from 1975 to 1990. She was the longest-serving British prime minister of the 20th century and the first woman to hold the position. As prime minister, she implemented economic policies known as Thatcherism. A Soviet journalist dubbed her the "Iron Lady", a nickname that became associated with her uncompromising politics and leadership style.