Charlton won 106 caps for England and scored 49 international goals – records for his country at the time.
During a 17-year first-team career with United he won three league titles, a European Cup and an FA Cup.
Charlton’s family said he “passed peacefully in the early hours of Saturday morning”.
He was hailed as “England’s greatest player” and “an undisputed legend” as tributes flowed.
In November 2020, it was announced Charlton had been diagnosed with dementia.
He died surrounded by his family, who said in a statement they wished to “pass on their thanks to everyone who has contributed to his care and for the many people who have loved and supported him”.
“We would request that the family’s privacy be respected at this time,” the statement added, as the family said his loss was felt “with great sadness”.
United said Charlton ranked as “one of the greatest and most beloved players in the history of our club”.
“Sir Bobby was a hero to millions, not just in Manchester, or the United Kingdom, but wherever football is played around the world,” the club said.