The 32-year old joins on a three-year deal and is Rangers' second signing since new owner Tony Fernandes completed his takeover, following midfielder Joey Barton to Loftus Road.
Young rejected a proposed move to Liverpool last summer but said he was happy to be a part of a club looking to nail down their place in the Premier League.
"I am ready for a new challenge," he told QPR's official website. "There are big things that are going to happen at this Football Club and I am really pleased to be a part of it.
"Myself and Joey [Barton] signing here shows the intent of the Club.
"I am really looking forward to getting started and pulling on the blue and white shirt."
Hoops boss Neil Warnock was delighted to add another experienced Premier League player to his squad.
"I've been looking for a defender with vast Premier League experience for a while now and Luke certainly fits the bill," said Warnock.
"He can play anywhere across the back four and that versatility will stand us in really good stead.
"Moving back home to London will also serve him well and I'm really looking forward to seeing him in action for us - he's got so much to give and his experience will be vital."