The midfielder moves to Loftus Road for an undisclosed fee and has put pen to paper on a three-year deal.
Signed from non-league side Marlow in 2013, Gladwin made his professional bow for the club against Stevenage in December 2013. He netted his first goal against Plymouth Argyle in October 2014 and notched a first senior hat-trick in Town's 4-2 win over Rochdale in April.
He scored twice in the second leg of Town's Play-Off semi-final thriller against Sheffield United and played 90 minutes at Wembley in the Play-Off Final.
Everyone at Swindon Town would like to thank Ben for his service to the club and wish him all the best in his future endeavours.