Born Margaret Roberts on October 13, 1925, the daughter of a grocer, she graduated from Somerville College, Oxford, with a degree in chemistry, although she had always had an interest in politics and law. She ran for Parliament in 1950 but lost and continued to work as a research chemist. The following year she married well-to-do businessman Dennis Thatcher. Her marriage enabled her to finish her studies for the bar and devote herself to politics. Although she again lost a bid to Parliament in 1951, she succeeded in winning the Conservative Finchely district seat in October 1959. Her first government posts were as joint parliamentary secretary of Pensions and National Insurance (1961-64) and as secretary of Education and Science (1970-74) under Prime Minister Edward Heath. After the Conservative Party lost two elections, however, Thatcher -- supported by the very conservative right wing of the party -- criticized Heath's economic policies and challenged him for leadership of the Conservative Party, which she won in February 1975.

In 1976, she indicated her foreign policy leanings when she criticized the Soviet Union for its failure to engage in "genuine detente," said Soviet intervention in Angola proved Soviet aims of world domination, and urged NATO to remain strong. Soon after, she was sarcastically called the "Iron Lady" by the Soviet press, but she chose to adopt the title, believing it illustrated her resolve and strength in the face of adversaries, as well as adversity. After the Conservatives won the May 1979 elections, Thatcher became the first woman prime minister of Britain. Her primary goal in her first term was to enact her ideas about how best to run the economy. She was saved from the unpopularity of her economic policies by her personal handling of the Falklands War with Argentina in 1982, which won her great popular acclaim. She rode this wave of patriotism to office in 1983, and a short upturn in the economy returned her to an unprecedented third term in office in 1987.

Throughout all three terms she pursued economic policies that reduced the power of the unions, decreased public spending, increased personal tax cuts, increased privatization of public utilities, and deregulated industry. Thatcher is recognized for having curbed runaway inflation, significantly reducing public spending and reducing the power of the British unions. However, her programs, known as "Thatcherism," also produced high unemployment (which nearly tripled in her first two terms), high interest rates and increased class differentiation, as well as growth of the underclass.

In foreign policy, she was a staunch anti-communist. A consistent supporter of NATO, she backed the 1979 decision to deploy U.S. Pershing and cruise missiles in Western Europe and took a tough line against the anti-nuclear demonstrators at Greenam Common, who tried to stop the delivery of the bulk of more than 160 missiles to be placed there. Thatcher also pressed ahead with her plans to modernize the British fleet with Trident II nuclear submarines and resisted Soviet efforts to include British and French nuclear deterrents in the INF treaty negotiations.

U.S. President Ronald Reagan, who took office in January 1981, proved to be Thatcher's ideological soul mate in both domestic and foreign policy. This ideological closeness produced intense transatlantic cooperation between the United States and Britain, especially on issues related to the Soviet Union. In December 1984, when Gorbachev visited London shortly before his elevation to general secretary of the Communist Party, Thatcher met with him. She came out of the discussions declaring, "I like Mr. Gorbachev -- we can do business together." She carried this message to Reagan, who had called the Soviet Union the "Evil Empire." By the fall of 1988, Thatcher declared that "the Cold War is over."

Despite winning the general election in 1987, Thatcher resigned in November 1990 in the face of increasing opposition concerning her economic policies. She held a parliamentary seat as a representative of Finchely until 1992, when she did not stand for re-election. She was made a baroness in 1992.