X Factor singer Tom Mann has been left devastated after his fiancée Dani Hampson, died suddenly on what would have been their wedding day.

Mann, 28, who appeared on the singing show in 2014, confirmed the sad news on social media.

Tom said he had lost the "love of his life" and would continue to wear his engagement ring as a "sign of unconditional love" for her.

The former Stereo Kicks member wrote in a heart-breaking post that his fiancée was the "best thing to have ever happened" to him and that he lost her on what should have been the happiest day of their lives.

Hampson, 34, had no apparent health issues and the cause of her death is yet to be publicly revealed. 

The couple share an eight-month-old son together.

"I can't believe I am writing these words but my darling Dani - my best friend, my everything and more, the love of my life - passed away in the early hours of Saturday morning, 18th June," Mann, wrote on Instagram, alongside a photo of Hampson holding their son, Bowie.

"What was supposed to be the happiest day of our lives ended in irreversible heartbreak. I feel like I have cried an ocean."

Mann continued, "We never made it to the alter; or got to say our vows, or dance our first dance, but I know you know that you were my entire world and the best thing that has ever happened to me, Danielle. I will wear this ring that I was always supposed to wear as a sign of my unconditional love to you."

The couple were supposed to get married in Sept. 2020 but were forced to postpone the ceremony due to the coronavirus pandemic. 

Hampson gave birth to Bowie in Oct. 2021.

Mann wrote that while he was "completely broken" by Hampson’s untimely demise, he was using "any strength I can muster" in order to be there for Bowie.

"I will not be a mark on the parent that you had already become but I promise I will do my everything to raise Bowie just the way we always wanted," Mann wrote.

"I promise you he will know how amazing his mummy was. I promise to make you so so proud," he said.

Mann described Hampson as "the most beautiful person inside and out" and "the most incredible soul." 

"We have lost such a special person and I am sure we are about to see an abundant outpouring of love that reflects that. I will try to find peace in your messages and comments, but right now I am grieving and I will be for a very, very long time."

He continued, "My darling Dani, the brightest light in any room, my world is nothing but darkness without you. I will miss you forever."

Tom Mann and Dani Hampson Dani Hampson died suddenly on June 18, on what would have been their wedding day. (image:@tommanninsta/Instagram).