The work by Graffiti Painters has been created on the outside wall of The Trafford pub.
The Red Devils legend, who made 758 appearances for the club,died at the age of 86last month.
The portrait was painted over the mural of former United player Cristiano Ronaldo.
Posting on Instagram, Graffiti Painters said: "Yesterday I said my bye to this legend up in Manchester."
The tribute comes in the same week final farewells were said to Sir Bobby at his funeral.
The Charlton family and friends were joined by leading figures from across the football world in the service on Monday.
Widely hailed as one of England's greatest ever players, Charlton was a key figure in the Three Lions' 1966 World Cup victory.
During a 17-year first team career with United he won three league titles, a European Cup and an FA Cup.
From 1958 to 1970 he played for England, and achieved 106 caps, a record-breaking 49 goals, the famous 1966 World Cup win, and a Ballon d'Or.
Sir Bobby Charlton: The First Gentleman of Football
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A mural in memory of Sir Bobby Charlton has been painted on the side of a pub near Manchester United's Old Trafford stadium.