Welbeck pens new four-year United deal
Welbeck's contract will keep him at Old Trafford until June 2016, extending his stay at a club he joined five years ago.
"Playing for United is all I've ever wanted to do - it's the club I've supported all my life," Welbeck told the club website.
"I can't wait for the challenge of the new season to play my part in helping the team compete for trophies."
The announcement follows on from the acquisition of Dutch striker Robin Van Persie, who completed his move from Arsenal last week.
The 21-year-old Welbeck has scored 17 times in 64 appearances for the club and enjoyed a breakout campaign last season after returning from a loan spell at Sunderland.