The 22-year-old has agreed terms on a three-year deal at Loftus Road and has left the Robins for an undisclosed fee.
Luongo scored six times and contributed eight assists during Swindon's run to the League One play-off final where they were beaten 4-0 by Preston on Sunday.
Ramsey is familiar with the midfielder having worked with him during the Australian international's time in Tottenham's academy.
Speaking to Rangers' official website, Ramsey said: "Mass is a player I know a lot about having played a part in his development at Spurs.
"He brings quality on the ball, the ability to link up play all across the pitch, and his goals and assists record at club and international level speaks volumes for a creative midfielder.
"As with any young player, there are areas of his game that need improving, but knowing him as I do, I know he will embrace the learning curve of playing for us in the Championship.
"I'm confident he will flourish at Loftus Road."
Luongo's arrival comes the day after QPR announced Joey Barton, Richard Dunne, Rio Ferdinand, Bobby Zamora, Shaun Wright-Phillips and Brian Murphy would all be leaving the club following their relegation from the top flight.
Rangers' new signing added: "Regular football is important to me, that's why QPR appealed to me
I'm at my best when I'm playing week in, week out - I'm all for playing as many games as possible in a season.
"The step up to the Championship is going to be a challenge, but I'll always back myself."
Later on Thursday afternoon, Rangers announced that Luongo's Swindon colleague Ben Gladwin had also moved to Loftus Road on a three-year contract.
The 22-year-old forward struck 11 times last term, with eight of them coming in the Robins' final seven fixtures.
Gladwin said: "I'm really pleased to be joining the club - and I'm really excited.
"There was interest from the Premier League but for me, personally, I think this move is a little more realistic at this stage of my career
Playing is what it's all about, sitting on the bench is no way to improve your game.
"Chris Ramsey is a fantastic coach and I'm sure he'll improve me on the training pitch
I spoke to him earlier this week and was hugely impressed by what he had to say and where he sees me fitting in."
Source : PA
Source: PA