Nathaniel O’Brien was killed in a car crash while driving on Barrier Highway, two hours north of Adelaide.
According to reports from South Australia Police, the teen had spent the morning performing at the Burra Country Music Festival, and he was on his way back to Adelaide to perform at a hotel there in the evening.
He is reported to have lost control of his car and crashed into a tree at about 11am on Sunday morning.
Nathaniel, who starred in the Australian version of The X Factor in 2014, tragically died at the scene.
He was the only person in the car at the time, and no one else was involved in the accident.
Dannii Minogue, appears as a judge on The X Factor Australia, led the tributes to Nathaniel on Twitter.
She tweeted: “So sad to hear about Nathaniel O'Brien.
“I remember him as such a warm, sunny person.”
She added: “My thoughts are with his family and friends.”
Her co-presenter Luke Jacobz also took to Twitter to share his grief over Nathaniel’s death, writing: “Ex XFactor contestant Nathaniel O'Brien sadly passed today.
“Thoughts and prayers are with his family and friends at this sad time.”
The judges also paid tribute to the up-and-coming star during a live episode of The X Factor in Australia - and it was clear that Dannii in particular was struggling to hold back her tears.
“There has been an outpouring on social media but I wanted to give our love to friends, family and everyone in South Australia,” she said emotionally.
The show's host Luke Jacobz added: “If you heard him sing, he had a voice of an angel.
“We're definitely thinking of you.”