Family spokesman Jim McGrath confirmed the death in a statement.
Mrs Bush brought a grandmotherly style to buttoned-down Washington, often appearing in her trademark fake pearl chokers and displaying no vanity about her white hair and wrinkles.
“What you see with me is what you get. I’m not running for president - George Bush is,” she said at the 1988 Republican National Convention, where her husband, then vice president, was nominated to succeed Ronald Reagan.
The Bushes, who were married January 6, 1945, had the longest marriage of any presidential couple in American history.
“I had the best job in America,” she wrote in a 1994 memoir describing her time in the White House. “Every single day was interesting, rewarding, and sometimes just plain fun.”
The publisher’s daughter and oilman’s wife could be caustic in private, but her public image was that of a self-sacrificing, supportive spouse who referred to her husband as her “hero”.
In the White House, “you need a friend, someone who loves you, who’s going to say, ‘You are great,’” Mrs Bush said in a 1992 television interview.
She was the matriarchal figure of a political dynasty that included two presidents - her husband George HW Bush and son George W Bush.
Eight years after leaving the nation’s capital, Mrs Bush stood with her husband as their son George W. was sworn in as president. They returned four years later when he won a second term.
Mrs Bush insisted she did not try to influence her husband’s politics.
“I don’t fool around with his office,” she said, “and he doesn’t fool around with my household.”
In her 1994 autobiography, Barbara Bush: A Memoir, Mrs Bush said she did her best to keep her opinions from the public while her husband was in office. But she revealed that she disagreed with him on two issues: she supported legal abortion and opposed the sale of assault weapons.
“I honestly felt, and still feel, the elected person’s opinion is the one the public has the right to know,” Mrs Bush wrote.
Mrs. Bush raised five children: George W., Jeb, Neil, Marvin and Dorothy. A sixth child, 3-year-old daughter Robin, died of leukaemia in 1953.
In a speech in 1985, she recalled the stress of raising a family while married to a man whose ambitions carried him from the Texas oil fields to Congress and into influential political positions that included ambassador to the United Nations, Republican party chairman and CIA director.
“This was a period, for me, of long days and short years,” she said, “of diapers, runny noses, earaches, more Little League games than you could believe possible, tonsils and those unscheduled races to the hospital emergency room, Sunday school and church, of hours of urging homework or short chubby arms around your neck and sticky kisses.”
Along the way, she said, there were also “bumpy moments - not many, but a few - of feeling that I’d never, ever be able to have fun again and coping with the feeling that George Bush, in his excitement of starting a small company and travelling around the world, was having a lot of fun.”