Manchester United defender Rafael has signed a new four-year contract that ties him to Old Trafford through the 2015-16 season.

The 21-year-old joined United, along with his twin brother Fabio, from Fluminense in 2008 and has since been capped on the international level by Brazil.

"Rafael is one of the club's brightest young prospects; he has no fear of playing and has great belief in himself," United manager Sir Alex Ferguson told the club's official website.

"The boy has developed immensely since joining United, his energy and enthusiasm are a joy to watch. Rafael has all the attributes to become one of the best fullbacks in the world and I am delighted he has signed a new contract."

Rafael appeared in 18 games in all competitions for the Red Devils last term as United finished level on points with champions Manchester City in the league but lost out on goal difference.

"I am so happy to sign a new contract. I love playing for Manchester United, there is a great team spirit here and a real desire to win," Rafael said.

"My time here has been unbelievable; winning two league titles, a league cup and a Club World Cup has made me hungry for more trophies. I would like to thank Sir Alex for his belief in me and I would also like to thank the fans for their support."