The first female prime minister of the United Kingdom was Margaret Thatcher. She served from May 4, 1979, to November 28, 1990, and was a member of the Conservative Party. Thatcher was known for her strong leadership style and economic policies, often referred to as "Thatcherism," which emphasized deregulation, privatization, and reducing the power of trade unions. Her tenure significantly impacted British politics and society, and she became a polarizing figure, often garnering both staunch supporters and fervent critics. Thatcher's legacy continues to influence conservative politics in the UK and beyond.