Thatcher led the Conservatives to three election victories, governing from 1979 to 1990, the longest continuous period in office by a British premier since the early 19th century.
A grocer´s daughter with a steely resolve, she was loved and loathed in equal measure as she crushed the unions, privatized vast swathes of British industry, clashed with the European Union and fought a war to recover the Falkland Islands from Argentine invaders.
She struck up a close relationship with U.S. President Ronald Reagan in the Cold War, backed the first President George Bush during the 1991 Gulf War, and declared that Soviet leader Mikhail Gorbachev was a man she could do business with.
Thatcher died peacefully on Monday morning, said Lord Bell, a spokesman for the family. She had been in poor health for months and had declined into dementia in her final years.
The British government said Thatcher would have a ceremonial funeral with military honors at London´s St Paul´s Cathedral, which falls short of a full state funeral, in accordance with the wishes of her family.