Romelu Lukaku officially completed his move from Everton to Manchester United on Monday for a reported fee of £75 million ($97m, 85.5m euros), a record deal between British clubs.
The 24-year-old Belgian international striker - Everton's record Premier League goalscorer - signed a five-year deal after passing his medical and agreeing personal terms which will see him earn over £200,000 a week.
"Romelu is a natural fit for Manchester United. He is a big personality and a big player. It is only natural that he wants to develop his career at the biggest club," said United manager Jose Mourinho on the club website.
"He will be a great addition to the group and I know they will make him very welcome. I am really looking forward to working with him again."
Lukaku thanked Everton and said he couldn't turn down a move to Manchester United.
"I would like to start by thanking Everton and the fans for the last four wonderful seasons, I have made some special friends and we have shared some amazing moments.
"However, when Manchester United and Jose Mourinho come knocking at the door it is an opportunity of a lifetime and one that I could not turn down. You could see the fight, determination and the spirit in this team during the Europa League final and I want to become a part of that.
"I cannot wait to run out at Old Trafford in front of 75,000 fans but before that pre-season is where the hard work starts and I am looking forward to that first training session."