The star, who launched his career with Wham! in the 1980s and later continued his success as a solo performer, is said to have “passed away peacefully at home”.
Thames Valley Police said South Central Ambulance Service attended a property in Goring in Oxfordshire at 13:42 GMT.
Police say they were treating the death as unexplained but there were no suspicious circumstances.
In a statement, Michael’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.”
On Instagram, Sir Elton John posted a photograph of himself with Michael, 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.”
Thames Valley Police said: “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.”
Treatment for pneumonia
Michael, who was born Georgios Kyriacos Panayiotou in north London, sold more than 100m albums throughout a career spanning almost four decades.
He first found fame with his schoolfriend Andrew Ridgeley in duo Wham! before going on to release solo albums, including the multi-million selling Faith and follow-up Listen Without Prejudice Vol. 1.
It outsold Faith in the UK but led to Michael losing a court case with record label Sony over his frustration over how the album has been marketed.
From teen idol to long-term stardom
His talents as a singer, songwriter and music producer made George Michael one of the world’s biggest-selling artists.
Blessed with good looks and a fine singing voice, his stage presence made him a favourite on the live concert circuit as he matured from teen idol to long term stardom.
But there were times when his battle with drugs and encounters with the police made lurid headlines that threatened to eclipse his musical talents.
Michael scored seven number one singles in the UK with songs including Careless Whisper and Faith, and won three Brit Awards and two Grammys.
But as his career faded, Michael faced headlines for the wrong reasons.
In October 2006 he pleaded guilty to driving while unfit through drugs and was banned from driving and in 2008 he was cautioned for possession of class A drugs, including crack cocaine.
In September 2010 Michael received an eight-week prison sentence following an incident the previous July in which he crashed his Range Rover into a shop in north London.
Pop stars from Michael’s heyday were joined by more contemporary names in paying tribute on Twitter.
ABC frontman Martin Fry said : “Absolutely devastated to hear of the loss of @GeorgeMichael Truly brilliant talent #sad #sad #sad.”
Duran Duran referred to the the so-called “curse of 2016” – following the deaths of David Bowie, Prince and Rick Parfitt – posting on their official Twitter account: “2016 – loss of another talented soul. All our love and sympathy to @GeorgeMichael’s family.”
The band included a picture of Michael with singer Simon Le Bon, Sting and Bob Geldof.
Singer Pixie Lott tweeted: “Grew up listening to the beautiful and talented @GeorgeMichael – my mama’s favourite! was a pleasure to meet him so sad to hear the news.”
Fellow pop star La Roux wrote: “Another one gone…. What a voice, what a songwriter.”
DJ Tony Blackburn said: “Unbelievable, George Michael has died at the age of 53. RIP.This dreadful year goes on and on. So sad, a real talent.”
Earlier this month it was announced that producer and songwriter Naughty Boy was working with Michael on a new album.
A documentary film entitled Freedom was also due for release next March.
In 2011, Michael postponed a series of concerts after being taken to hospital for treatment for pneumonia.
After 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 were said to have performed a tracheotomy to keep his airways open and he was unconscious for some of his spell in hospital.
After years of refusing to be drawn on speculation about his sexuality, Michael disclosed he was gay in 1998 after being was arrested in a public toilet in Beverly Hills, California, for engaging in a lewd act.
George Michael’s UK number one singles
- Wake Me Up Before You Go Go (with Wham!) – 1984
- Freedom (with Wham!) – 1984
- Careless Whisper – 1984
- I’m Your Man (with Wham!) – 1985
- The Edge of Heaven (with Wham!) – 1986
- A Different Corner – 1986
- I Knew You Were Waiting For Me (with Aretha Franklin) – 1987
- Don’t Let the Sun Go Down on Me (with Elton John) – 1991
- Five Live EP (with Queen and Lisa Stansfield) – 1993
- Jesus To A Child – 1996
- Fastlove – 1996