Margaret Hilda Thatcher, Baroness Thatcher, (1925 - 2013) was a British stateswoman who was the Prime Minister of the United Kingdom from 1979 to 1990 and the 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 have held the office. A Soviet journalist dubbed her The Iron Lady, a nickname that became associated with her uncompromising politics and leadership style. As Prime Minister, she implemented policies that have come to be known as Thatcherism.