Winger Ashley Young has signed a five-year contract with Manchester United after they agreed a fee with Aston Villa.
The 25-year-old England international underwent a medical on Wednesday and the transfer, reported to be worth between £16million and £20million, was finalised on Thursday.
He becomes Sir Alex Ferguson's second signing of the summer after the capture of England Under-21 international Phil Jones from Blackburn for £16.5million.
Villa signed Young from Watford in January 2007 in a deal eventually worth £10million and he went on to score 38 goals in 190 appearances.
However, he made it clear to Villa he would not be signing an extension to his contract, which was due to expire next summer, and the club had little alternative but to sell one of their prize assets.
"Ashley has made a terrific contribution for Villa over the past four and a half seasons and everyone at the club wishes him the best for the future," new Villa manager Alex McLeish said.
"He has become an important player in the England team during that time and I'm sure he will be looking forward to this new challenge."
Young said the lure of Old Trafford proved too much for him to consider remaining at Villa. He told MUTV: "The opportunity to come and play for one of the biggest clubs in the world is one I couldn't turn down.
"It's a chance to hopefully become part of their history by helping to win the 20th title.
"It's a prospect I always looked at from being a child: to play for one of the biggest clubs in the world. I've got that opportunity now so I've just got to take it with two hands."