Bush was the wife of the 41st president, George H.W. Bush, and mother of the 43rd, George W. Bush.
The Bush family had announced in a statement on April 15 that she was in failing health and had decided not to seek further medical treatment.
She reportedly had been battling chronic obstructive pulmonary disease and congestive heart problems in recent years.
“He held her hand all day today and was at her side when [she] left this good earth,” the former president’s chief of staff Jean Becker said.
Barbara Bush was dubbed “The Silver Fox” by her husband and children.
She was known for her snow-white hair and for being fiercely protective of her family.
She was first lady when her husband was in the White House from 1989 to 1993.
Her son, Republican George Walker Bush, triumphed in the disputed 2000 US election and was president from 2001 to 2009.
The father-and-son presidents were sometimes referred to as “Bush 41” and “Bush 43.”
The Bushes had celebrated their 73rd wedding anniversary in January 2018.
She discouraged speculation that she wielded political influence with the president.
“I don’t fool around with his office and he doesn’t fool around with my household,” she once said.
“She’ll speak her mind but only to him,” said Jack Steel, a longtime Bush aide.