A statement from the office of her husband, former president George HW Bush, described her as a "relentless proponent of family literacy".
Mrs Bush, the only woman to have seen her husband and son sworn in as US president, had been unwell for some time and had declined further medical treatment.
She said she wanted to spend her last days in "comfort care" with her family.
Her husband, at 93, is the longest-lived US president.
Their son, George W Bush, was elected president in 2000 and served two terms as the nation's 43rd president.
He said in a statement: "My dear mother has passed on at age 92. Laura, Barbara, Jenna, and I are sad, but our souls are settled because we know hers was. Barbara Bush was a fabulous First Lady and a woman unlike any other who brought levity, love, and literacy to millions."
Mr Bush said his mother had "kept us on our toes and kept us laughing until the end", adding: "I'm a lucky man that Barbara Bush was my mother. Our family will miss her dearly, and we thank you all for your prayers and good wishes."
In a statement, Bill and Hillary Clinton said Mrs Bush was "feisty in support of her family and friends, her country and her causes".
George HW Bush, who served as the 41st US president from 1989-93, suffers from a form of Parkinson's disease and uses a wheelchair.
He and Barbara Bush were married for 73 years.
It was recently announced that Mrs Bush had declined further medical treatment after a series of hospital visits, but the statement did not reveal the nature of her ailments.