Mads Glæsner (born 18 October 1988, Tårnby) is a Danish swimmer.
He participated at the 2008 Summer Olympics in the 400 metre freestyle and the 1500 metre freestyle disciplines.
His swimming club is Vallensbæk-VAT but he trains at the National Training Center in Copenhagen.
He competed at the 2012 Summer Olympics in the 400 m freestyle and the 4 x 200 m freestyle relay.In June 2013, Glæsner was stripped of a gold and bronze medal from the 2012 World Short Course Championships after testing positive for levomethamphetamine.However, upon appeal to the Court of Arbitration for Sport, Glaesner's 1500-metre freestyle gold medal was reinstated based on the fact that a test after that race, two days after his initial positive test following the 400-metre free, was clean.
He still forfeited the 400-metre freestyle bronze, which he did not appeal.Since then, he has competed at the 2016 Summer Olympics, in the 400 m freestyle.