The famous female British prime minister known as the "Iron Lady" is Margaret Thatcher. She served as the Prime Minister of the United Kingdom from 1979 to 1990 and was the leader of the Conservative Party. Thatcher earned the nickname "Iron Lady" due to her strong and uncompromising leadership style, especially in economic and foreign policy matters. She was known for her free market policies, reducing the power of trade unions, and her close relationship with U.S. President Ronald Reagan during the Cold War. Her tenure left a significant impact on British politics and society, often leading to polarized opinions about her legacy.