The actor is believed to have had terminal cancer, but his spokespeople have refused to confirm this.
A statement from his representative said: "We formally announce the loss of Leslie Grantham, who passed away at 10.20am on the morning of Friday 15th June 2018.
"His ex-wife and sons have asked for their privacy to be respected at this difficult time, and for there to be no approaches to them for information or comment.
"There will be a private funeral which will be attended by close family and friends only."
He fell ill after returning to the UK from Bulgaria where he'd been living since 2013.
A close friend said before his death: “Leslie is being looked after.
"Those who are close to him are hugely worried and are praying for his well-being.”
Leslie married Jane Laurie in 1981, but the pair divorced in 2013 - he is survived by their three children.
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Leslie as Dirty Den in EastEndersCredit: Handout
What was Leslie Grantham's murder conviction?
In 1966, Grantham attempted to rob a taxi driver in West Germany.
Following a struggle between the two, the driver ended up dead with a gunshot to the head.
Leslie told police upon his arrest that he didn't know the gun was loaded.
However, at his trial a year later, the jury found him guilty of murder and he was sentenced to life imprisonment.
After serving 10 years of his sentence, Grantham was released in 1977.
How long did Leslie Grantham play Dirty Den?
During his time in prison, Grantham took part in several productions and plays, and was encouraged to pursue acting.
He trained at the Webber Douglas Academy of Dramatic Art in London before taking part in Jake's End, Goodnight and God Bless and Resurrection of the Daleks.
The actor rose to fame when he was signed for the role of "Dirty" Den Watts in EastEnders in 1985.
His character was a notorious womaniser and owner of the Queen Vic pub with his wife Angie Watts.
In a dramatic Christmas Day special in 1986, he signed the divorce papers with Happy Christmas Ange, before handing the Vic over to Frank Butcher.
Grantham then wished to leave the soap after hearing co-star Anita Dobson was leaving the Square.
He exited in 1989, as viewers watched a mysterious gunman shoot him down, presuming he was dead.
It wasn't until 14 years later, in September 2003, that Dirty Den returned - surprising the residents of Walford and his adopted daughter Sharon.
He then left again in February 2005, as new wife Chrissie hit him over the head with a statue of a dog.
