The Sun says Ferguson snapped up Young in a £20million swoop last night.
It took Manchester United's summer spending to a whopping £55m - leaving their title rivals in the shade.
The arrival of Aston Villa's England star Young completes an astonishing hat-trick of Ferguson buys worth £55m as he begins to build a new dynasty.
Young, 25, passed a medical at the club's Carrington Training Ground yesterday and put pen to paper on a four-year contract.
He now joins Phil Jones who moved on Wednesday from Blackburn to Old Trafford in a £16.5m transfer.
And a deal has also been agreed for Spanish goalkeeper David De Gea to move from Atletico Madrid to United for £18.5million.