The Red Devils legend has hailed the iconic manager, who added a 13th league title to his reign at Old Trafford on Monday.
United beat Aston Villa 3-0 on Monday to regain the Premier League title from Manchester City with four games remaining - making it 13 league titles under Ferguson during his 27-year reign at Old Trafford.
"He's been marvellous and everything that Manchester United wanted. He's been a major success and is the greatest manager there's ever been. It's unquestioned," Charlton told reporters.
"He is such a motivator and he's in control totally of his squad. I'm happy just to say 'on you go, Al, you just do it the way you've always done it'.
"It shows in the performances and the goals that we're scoring. We have lots and lots of goalscorers now and most of them are pretty young, so the future looks pretty good.
"He reads the game and knows the game. He finds that young players are really important in the future of the club.
"Then when you've got someone like Robin van Persie, at 29, he has been a success. Alex wants the younger players who come through to be that successful too.
"How he does it is a question of talent that only Alex can answer. He knows everything about the game."