Margaret Hilda Roberts was born on 13 October 1925, in Grantham, Lincolnshire.
Roberts graduated From Oxford in 1947 with Second-Class Honours, in the four-year Chemistry Bachelor of Science degree, specialising in X-ray crystallography under the supervision of Dorothy Hodgkin. Her dissertation was on the structure of the antibiotic gramicidin.
Roberts joined the local Conservative Association and attended the party conference at Llandudno, Wales, in 1948, as a representative of the University Graduate Conservative Association.
One of her Oxford friends was also a friend of the Chair of the Dartford Conservative Association in Kent, who were looking for candidates. Officials of the association were so impressed by her that they asked her to apply, even though she was not on the party's approved list; she was selected in January 1950 (aged 24) and added to the approved list post ante.
In the 1950 general elections, Roberts was the Conservative candidate for the safe Labor seat of Dartford. The local party selected her as its candidate because, though not a dynamic public speaker, Roberts was well-prepared and fearless in her answers. She attracted media attention as the youngest and the only female candidate, but she lost to Norman Dodds.She lost again in the 1951 general elections.
At a dinner following her formal adoption as Conservative candidate for Dartford in February 1949 she met divorcé Denis Thatcher, a successful and wealthy businessman, who drove her to her Essex train. After their first meeting she described him to Muriel as "not a very attractive creature – very reserved but quite nice". They married on 13 December 1951, at Wesley's Chapel in City Road, London.
In 1954, Thatcher was defeated when she sought selection to be the Conservative party candidate for the Orpington by-election of January 1955.
Thatcher began looking for a Conservative safe seat and was selected as the candidate for Finchley in April 1958 (narrowly beating Ian Montagu Fraser).
She was elected as MP for the seat after a hard campaign in the 1959 election.
In October 1961 she was promoted to the frontbench as Parliamentary Undersecretary at the Ministry of Pensions and National Insurance by Harold Macmillan. Thatcher was the youngest woman in history to receive such a post, and among the first MPs elected in 1959 to be promoted.
After the Conservatives lost the 1964 election she became spokesman on Housing and Land, in which position she advocated her party's policy of allowing tenants to buy their council houses.
In 1967, the United States Embassy in London chose Thatcher to take part in the International Visitor Leadership Program (then called the Foreign Leader Program), a professional exchange programme that gave her the opportunity to spend about six weeks visiting various US cities and political figures as well as institutions such as the International Monetary Fund. Following the visit, Heath appointed Thatcher to the Shadow Cabinet as Fuel and Power spokesman.
Thatcher made her first visit to the Soviet Union in the summer of 1969 as the Opposition Transport spokeswoman.
Prior to the 1970 general election, she was promoted to Shadow Transport spokesman and later to Education.
The Conservative Party led by Edward Heath won the 1970 general election, and Thatcher was subsequently appointed to the Cabinet as Secretary of State for Education and Science. Thatcher caused controversy when after only a few days in office she withdrew Labour's Circular 10/65 which attempted to force comprehensivisation, without going through a consultation progress.
Heath's leadership of the Conservative Party looked increasingly in doubt. Thatcher was not initially seen as the obvious replacement, but she eventually became the main challenger, promising a fresh start. Her main support came from the parliamentary 1922 Committee and The Spectator. She defeated Heath on the first ballot and he resigned the leadership. In the second ballot she defeated Whitelaw, Heath's preferred successor. Thatcher became Conservative Party leader and Leader of the Opposition on 11 February 1975; she appointed Whitelaw as her deputy.
The Labour government then faced fresh public unease about the direction of the country and a damaging series of strikes during the winter of 1978–79, dubbed the "Winter of Discontent". The Conservatives attacked the Labour government's unemployment record, using advertising with the slogan "Labour Isn't Working". A general election was called after the Callaghan ministry lost a motion of no confidence in early 1979. The Conservatives won a 44-seat majority in the House of Commons and Thatcher became the first female British prime minister.
On 6 November 1981, Thatcher and Irish Taoiseach Garret FitzGerald had established the Anglo-Irish Inter-Governmental Council, a forum for meetings between the two governments.
In September 1982 she visited China to discuss with Deng Xiaoping the sovereignty of Hong Kong after 1997. China was the first communist state Thatcher had visited and she was the first British prime minister to visit China.
The "Falklands factor", an economic recovery beginning early in 1982, and a bitterly divided opposition all contributed to Thatcher's second election victory in 1983.
Thatcher narrowly escaped injury in an IRA assassination attempt at a Brighton hotel early in the morning on 12 October 1984. Five people were killed, including the wife of minister John Wakeham. Thatcher was staying at the hotel to prepare for the Conservative Party conference, which she insisted should open as scheduled the following day.
On 15 November 1985, Thatcher and FitzGerald signed the Hillsborough Anglo-Irish Agreement, which marked the first time a British government had given the Republic of Ireland an advisory role in the governance of Northern Ireland.
By 1987, unemployment was falling, the economy was stable and strong and inflation was low. Opinion polls showed a comfortable Conservative lead, and local council election results had also been successful, prompting Thatcher to call a general election for 11 June that year, despite the deadline for an election still being 12 months away. The election saw Thatcher re-elected for a third successive term.
Thatcher was challenged for the leadership of the Conservative Party by the little-known backbench MP Sir Anthony Meyer in the 1989 leadership election. Of the 374 Conservative MPs eligible to vote, 314 voted for Thatcher and 33 for Meyer. Her supporters in the party viewed the result as a success, and rejected suggestions that there was discontent within the party.
On 1 November 1990, Howe, by then the last remaining member of Thatcher's original 1979 cabinet, resigned from his position as Deputy Prime Minister, ostensibly over her open hostility to moves towards European Monetary Union.
On 14 November, Michael Heseltine mounted a challenge for the leadership of the Conservative Party. Opinion polls had indicated that he would give the Conservatives a national lead over Labour. Although Thatcher led on the first ballot with the votes of 204 Conservative MPs (54.8%) to 152 votes (40.9%) for Heseltine and 16 abstentions, she was four votes short of the required 15% majority. A second ballot was therefore necessary. Thatcher initially declared her intention to "fight on and fight to win" the second ballot, but consultation with her Cabinet persuaded her to withdraw. After holding an audience with the Queen, calling other world leaders, and making one final Commons speech, on 28 November she left Downing Street in tears. She reportedly regarded her ousting as a betrayal. Her resignation was a shock to many outside Britain, with such foreign observers as Henry Kissinger and Gorbachev expressing private consternation.
Thatcher returned to the backbenches as a constituency parliamentarian after leaving the premiership. Aged 66, she retired from the House at the 1992 general election, saying that leaving the Commons would allow her more freedom to speak her mind.
After retiring from the Commons in 1992, she was given a life peerage as Baroness Thatcher (of Kesteven in the County of Lincolnshire) which entitled her to sit in the House of Lords.
On 26 June 2003, Thatcher's husband Sir Denis died of pancreatic cancer, and was cremated on 3 July at Mortlake Crematorium in London.
After collapsing at a House of Lords dinner, Thatcher, suffering low blood pressure, was admitted to St Thomas' Hospital in central London on 7 March 2008 for tests.
She last attended a sitting of the House of Lords on 19 July 2010.
On 30 July 2011 it was announced that her office in the Lords had been closed.
Baroness Thatcher died on 8 April 2013, at the age of 87, after suffering a stroke.
Details of Thatcher's funeral had been agreed with her in advance. She received a ceremonial funeral, including full military honours, with a church service at St Paul's Cathedral on 17 April. Queen Elizabeth II and the Duke of Edinburgh attended her funeral, marking only the second time in the Queen's reign that she attended the funeral of any of her former prime ministers.