Popstar George Michael has died peacefully at his home, his publicist has said.
The 53-year-old, who was set to release a documentary in 2017, rose to fame as a member of Wham!, known for their hits Club Tropicana and Last Christmas.
Michael - whose real name was Georgios Kyriacos Panayiotou - sold more than 100 million albums throughout a career spanning almost four decades.
In a statement, the star's publicist said: "It is with great sadness that we can confirm our beloved son, brother and friend George passed away peacefully at home over the Christmas period.
"The family would ask that their privacy be respected at this difficult and emotional time. There will be no further comment at this stage."
Michael's former partner Kenny Goss said he was "heartbroken" about the death of his "dear friend and long-time love", adding: "He was a major part of my life and I loved him very, very much."
Big names from the world of entertainment have paid tribute to him after hearing about his death, which comes in a year that has seen the music industry lose some of its biggest stars including Prince, David Bowie and Leonard Cohen.
— RTÉ News (@rtenews) December 26, 2016
Elton John posted a photograph of himself and Michael on Instagram, writing: "I am in deep shock. I have lost a beloved friend - the kindest, most generous soul and a brilliant artist. My heart goes out to his family and all of his fans."
Michael's former Wham! bandmate Andrew Ridgeley said he was "heartbroken at the loss of my beloved friend Yog", a nickname which refers to "Yours Only George".
He said: "Me, his loved ones, his friends, the world of music, the world at large. 4ever loved. A xx."
Friend Madonna paid her own tribute, posting an undated video on Twitter in which she embraced Michael on stage. In it she tells the audience: "He's a great songwriter and he makes very classy videos, like me."
Referencing several of his best known lyrics, she adds: "George, I want your sex, so be my father figure and I will have faith if we have to live hand-to-mouth. The diva himself."
Former Beatle Paul McCartney, who worked with Michael on the 2006 release Heal The Pain, also paid tribute.
He said: "George Michael's sweet soul music will live on even after his sudden death. Having worked with him on a number of occasions his great talent always shone through and his self deprecating sense of humour made the experience even more pleasurable."
Michael formed duo Wham! with Ridgeley in 1981, and went on to massive success, releasing a string of hit singles including Wham Rap! (Enjoy What You Do), Club Tropicana, Wake Me Up Before You Go Go, and Last Christmas.
They were the first Western pop act to visit China when they played there in 1985, before splitting in 1986, by which time Michael had already released a handful of solo singles.
Thames Valley Police said they were called to a property in Goring-on-Thames shortly before 2pm (on Christmas Day), adding: "Sadly, a 53-year-old man was confirmed deceased at the scene.
"At this stage the death is being treated as unexplained but not suspicious. A post-mortem will be undertaken in due course. There will be no further updates from Thames Valley Police until the post-mortem has taken place."
As well as being known for his talents, Michael had a turbulent personal life, as brushes with the law and tales of drug use saw him hit the headlines.
Michael nearly died from pneumonia in late 2011.
After receiving treatment in a Vienna hospital, he made a tearful appearance outside his London home and said it had been "touch and go" whether he lived.
Doctors had performed a tracheotomy to keep his airways open and he was unconscious for some of his spell in hospital.
Earlier this month, it was reported that songwriter and producer Naughty Boy was working with Michael on the legend's new album. Speaking at the BBC Music Awards, Naughty Boy said: "I can't wait. I don't know what to expect. And, to be honest, he's more mysterious than anyone else so I'm actually excited."
Meanwhile, Michael's 1990 album Listen Without Prejudice Vol. 1 had been set to be reissued accompanied by a new film featuring Stevie Wonder, Elton John and the supermodels who starred in the video to his hit single Freedom! '90.
The movie, with the working title Freedom: George Michael, was to be narrated by Michael and was set to feature Mark Ronson, Mary J Blige, Tony Bennett, Liam Gallagher, James Corden and Ricky Gervais.
The record was his second solo album, after the hugely successful Faith, and was arranged, produced and almost entirely written by Michael, but did not feature him on the album cover.
It featured hits including Cowboys And Angels, Mother's Pride and Praying For Time and outsold Faith in the UK, where it went platinum four times but led to a court case with US record label Sony about Michael's frustration over how the album had been marketed. Michael lost the case.