Scott Marsden needed urgent medical attention during the competition on Saturday and was taken to hospital where his condition was described as critical.
Leeds Martial Arts College paid tribute to the "true champion".
"Our deepest condolences & sympathy go to our friends the Marsdens at this terrible time," it said in a statement.
"Scotty will always be in our hearts & our thoughts & we miss you dearly.
"A true champion in every way who's energy & positivity affected everyone he met.
"Rest now Scotty lad."
The teenager had been kickboxing since the age of four and was a pupil at Forge Valley secondary school in Sheffield.
He was a member of Marsden's All Styles Kickboxing, which has set up a JustGiving page to raise money for the youngster's family.
Charlotte Rowlett, who set up the site, said: "Everything Scotty did he did with passion and a confidence that was a pleasure to behold.
"He was the most wonderful, talented boy and the loss of him will leave a hole in so many people's lives.
"Scott was not only a kick boxer though, he is a son, a brother, a grandson, a nephew, a cousin and a friend."
On the night of the contest, Marden's All Styles Kickboxing described on Facebook how the fight came to be stopped.
"Unfortunately, (Saturday) night's English title fight had to be stopped due to Scotty needing immediate medical attention," the club wrote.
It continued: "There was no way to foresee the fight ending in such a way as at no point were either ever in any overwhelming danger from each other.
"Everyone is still in shock as there were simply no signs to suggest the fight needed to be stopped.
"The referee stepped in to protect Scott as soon as he could, which meant Scott did not hit the canvas and was laid down and straight into recovery position."
Police are investigating the circumstances of his death, but have said they are not treating it as suspicious.
World Kickboxing Association (WKA) England president Jon Green posted on Facebook: "Not just WKA but the world of kickboxing is mourning such a well-loved and respected fighter and sportsman."