The South Korean, who joined the Red Devils from PSV Eindhoven in 2005, officially announced his departure to Loftus Road on Monday for an undisclosed fee.
And the four-time Premier League-winning midfielder described playing for the Old Trafford outfit as a "privilege".
"My time at United will last in my heart for the rest of my life," he told the club's official website.
"It’s been a great privilege to be part of such a great team, to have won so much and to have played with special teammates and for the greatest manager in the game.
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|6.50||QPR are 6.50 with bet365 to be relegated next season|
"I would like to thank everybody at the club who give their best every single day to put every player in the best condition to enjoy their football and achieve success."
Park, who enjoyed cult status amongst the club's fans, also had kind words for the Old Trafford faithful upon his departure.
“The fans have been fantastic to me and I will always remember them with great affection," he added.
"Now, I’m looking forward to giving everything for a new challenge at QPR, where I will bring all my ambition and spirit I have gathered at United. [Those qualities] will be with me forever."