Park has become a key member of the United squad after there was doubts about him when Sir Alex signed him from PSV Eindhoven in 2005.
It was a couple of weeks ago that Park agreed to sign a new deal while the team was on tour of North America, now the deal has been made complete before Sunday’s opening game.
"I have enjoyed every minute of my time at United," said the 30 year old.
"I am delighted to be part of the club during this latest stage in its history - with another exciting young team being built.
"I am looking forward to playing my part in keeping United at the top of the game."