"The X Factor" star Tom Mann suffered a horrible tragedy over the weekend ... his fiancee died just hours before their wedding.

Dani Hampson, a 34-year-old publicist, had no apparent health issues and the cause of her death has not been revealed.

She had posted pics of her and Tom, along with their 8-month-old son Bowie, just days before she died.

Tom and Dani were actually supposed to get married Sept. 25, 2020, but the pandemic got in the way. At the time she posted, "I can't wait to marry you, but the world has other plans."

Dani also had posted a video of Tom -- a member of the group Stereo Kicks -- singing Elton John and Dua Lipa's song, "Cold Heart."

She used the song to wish Bowie, "Happy 6 months my darling boy." She wrote, "I played this song almost every day of my 3rd trimester, it was in my labour playlist & it was number 1 the day Bowie was born… determined for it to be "our song" & for it always remind us of life's good bits."

Tom announced Dani's death Monday, calling her the "brightest light in any room," adding he will miss her forever. He told his followers, "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. On what was supposed to be the happiest day of our lives ended in irreversible heartbreak."

He went on to say, "I am completely broken trying to process this and I honestly don't know where to go from here, but I do know I need to use any strength I can muster for our little boy."

Tom auditioned as a solo singer for 'X Factor' back in 2014, but producers created the group, Stereo Kicks, of which he was a member.

Dani was 34.

RIP