The Grammy award-winning soul singer struggled with well-documented alcohol and drug addictions but her death is being treated as unexplained.
"Police were called by London Ambulance Service to an address in Camden Square shortly before 4:05 pm (1505 GMT) today, Saturday 23 July, following reports of a woman found deceased," a police statement said.
"On arrival officers found the body of a 27-year-old female who was pronounced dead at the scene ... Enquiries continue into the circumstances of the death."
London Ambulance Service had been called to the flat at 3:54 pm (1454 GMT) and sent two ambulances.
Winehouse rocketed to fame after winning five Grammy awards off the back of her 2006 second album "Back to Black" and the hit single "Rehab".
In the run-up to her live return, Winehouse spent a week at an addiction treatment clinic in London, reportedly at the suggestion of her father, Mitch, over concerns that she was drinking too much before her shows.
But Winehouse pulled out of her European comeback tour following a disastrous opening performance in Serbia on June 18. She was booed at the performance in Belgrade, as she appeared to be too drunk to sing.
Some 20,000 people gathered for the highly-promoted concert at the sixth-century Kalemegdan fortress, but many soon left.
During the concert, which lasted about 90 minutes, Winehouse could only mumble some of the lyrics, failing to follow her band. Winehouse left the stage twice, with many fans showing their displeasure despite her band's attempts to calm the crowd.
She had also been scheduled to perform in Istanbul, Athens, Bilbao in Spain, Locarno in Switzerland, Italy's Lucca festival, Switzerland's Paleo Festival in Nyon, Nova Jazz and Blues Night in Wiesen, Austria, and Poland's Bydgoszcz Artpop Festival.
'Jewish Salt 'n' Pepa'
With her black beehive hairdo and old-fashioned sailor tattoos, Winehouse was one of pop music's most recognisable stars.
Born in 1983 to taxi driver Mitch Winehouse and his pharmacist wife Janis, Winehouse grew up in the north London suburbs, and was set on a show business career from an early age.
When she was 10, she and a friend formed a rap group, Sweet 'n' Sour - Winehouse was Sour - that she later described as "the little white Jewish Salt 'n' Pepa".
She attended the Sylvia Young Theatre School, a factory for British music and acting moppets, later went to the Brit School, a performing arts academy in the "Fame" mold, and was originally signed to Simon Fuller's 19 Management "Pop Idol".
But Winehouse was never a packaged teen star, and always resisted being pigeonholed.
Her jazz-influenced 2003 debut album, "Frank", was critically praised and sold well in Britain.
Winehouse soon expressed dissatisfaction with the disc, saying she was "only 80 per cent behind" the album and self-destructive habits began to overshadow her distinctive musical talent.
In the end, the music was overshadowed by fame, and by Winehouse's demons. Tabloids lapped up the erratic stage appearances, drunken fights, stints in hospital and rehab clinics.
'Just a musician'
Performances became shambling, stumbling train wrecks, watched around the world on the internet.
"Frank" was followed by a slump during which Winehouse broke up with her boyfriend, suffered a long period of writer's block and, she later said, smoked a lot of marijuana.
"At one point it had been two years since the last record and (the record company) actually said to me, 'Do you even want to make another record?' I was like, 'I swear it's coming.' I said to them, 'Once I start writing I will write and write and write. But I just have to start it'."
The album she eventually produced was a sensation. "I didn't go out looking to be famous," Winehouse told the Associated Press news agency after her most successful album was released in 2006. "I'm just a musician."
Working with producers Mark Ronson and Salaam Remi and soul-funk group the Dap-Kings, Winehouse fused soul, jazz, doo-wop and, above all, a love of the girl-groups of the early 1960s with lyrical tales of romantic obsession and emotional excess.
Increasingly, her personal life began to overshadow her career and she acknowledged struggling with eating disorders and told a newspaper that she had been diagnosed as manic depressive but refused to take
In May 2007 in Miami, she married music industry hanger-on Blake Fielder-Civil, but the honeymoon was brief.
That November, Fielder-Civil was arrested for an attack on a pub manager the year before but British newspapers reported extramarital affairs while Fielder-Civil was behind bars. They divorced in 2009.
Tragic '27 Club'
Winehouse's health often appeared fragile. In June 2008 and again in April 2010, she was taken to hospital and treated for injuries after fainting and falling at home.
Her father said she had developed the lung disease emphysema from smoking cigarettes and crack, although her spokeswoman later said Winehouse only had "early signs of what could lead to emphysema".
Music historians will note that has now become part of the tragic "27 club" of musicians who have died at that age - a roster that includes Jimi Hendrix, Janis Joplin, The Doors singer Jim Morrison and Nirvana frontman Kurt Cobain.
Mark Ronson, the disc jockey who produced more than half of the songs on "Black to Black", once said Winehouse was a refreshing antidote to bland pop.
"Amy is bringing a rebellious rock and roll spirit back to popular music," he said.