Margaret Thatcher was the first female Prime Minister of the United Kingdom, serving from 1979 to 1990. Known as the 'Iron Lady,' she was a member of the Conservative Party and implemented significant economic reforms that emphasized deregulation and privatization, which transformed the British economy. Thatcher's leadership style was characterized by her strong will and determination, often leading to both admiration and criticism. Her policies, known as 'Thatcherism,' focused on reducing the power of trade unions and promoting free-market principles, leaving a lasting impact on British politics and society.