Astor, recently the center of a highly publicized legal dispute over her care, died of pneumonia at Holly Hill, her Westchester County estate in Briarcliff Manor, family lawyer Kenneth Warner said.
"Brooke was a truly remarkable woman and an irreplaceable friend," longtime family friend David Rockefeller said. "She was the leading lady of New York in every sense of the word."
New York City Mayor Michael Bloomberg says Astor was the quintessential New Yorker and all are saddened by her death. Bloomberg, who has said that he plans to make philanthropy his next career, also praises her good will and kind nature and says New York would not be what it is today without her gracious support.
Astor, says Nancy Reagan, was a great lady. "We'll not see the likes of her again," said the former first lady.
Although a legendary figure in New York City and feted with a famous gala on her 100th birthday in March 2002, Astor was mostly interested in putting the fortune that husband, Vincent Astor, left to use where it would do the most to alleviate human misery.
Her efforts won her a Presidential Medal of Freedom, the nation's highest civilian honor, in 1998.
"Money is like manure, it should be spread around" - a line from a Thornton Wilder play - was Astor's oft-quoted motto. There was a lot to spread: Vincent Astor's great-great-grandfather John Jacob Astor made a fortune in fur trading and New York real estate.
But she also funded scores of smaller projects: Harlem's Apollo Theater; a new boiler for a youth center; beachside bungalow preservation; a church pipe organ; furniture for homeless families moving in to apartments.
It was a very personal sort of philanthropy.
"People just can't come up here and say, `We're doing something marvelous, send a check,"' she said. "We say, 'Oh, yes, we'll come and see it."'
The final year of Astor's life was marred by a family feud over her care, including allegations that the grand dame of society was forced to sleep on a couch that smelled of urine while subsisting on a diet of pureed peas and oatmeal. Court papers said her beloved dogs Boysie and Girlsie were kept locked in a pantry.
The allegations emerged in July 2006 court documents that provided a daily source of sensational headlines. In a settlement three months later, her son, Anthony Marshall, was replaced as her legal guardian with Annette de la Renta, wife of the fashion designer Oscar de la Renta.