Brazilian full-back Rafael, 21, has signed a new four-year contract that will keep him at Manchester United until 2016.
"Rafael is one of the club's brightest young prospects. He has no fear of playing and has great belief in himself," manager Alex Ferguson told the club's website on Monday.
Meanwhile, Rafael's twin brother Fabio has signed a season-long loan with QPR, the London club have announced.
United have also officially confirmed the release of striker Michael Owen and goalkeeper Tomas Kuszczak after their contracts expired, along with 18-year-old keepers Liam Jacob and Joe Coll.
Kuszczak has already joined npower Championship side Brighton while Jacob has gone to Oldham.
Owen is yet to find a club but has been linked with the short move to fellow Premier League side Stoke, close to where his horse racing stables are located.
