It has been the title long-associated with the late Prince Philip who was handed it before his wedding to the Queen.
But since his death - and that of the late monarch - there has been much speculation about who will be the next Duke of Edinburgh.
It's long been believed that Philip's youngest son Prince Edward would receive the title - making his wife Sophie Wessex, Duchess of Edinburgh.
But reports have suggested King Charles is not keen on this idea - and the dukedom may even be handed to his eldest granddaughter Princess Charlotte. Here we take a look at the title and who could be in line for it...
Duke of Edinburgh title
The title Duke of Edinburgh dates back to 1726 when it was first created by George I for his grandson Prince Frederik.
Upon his death, it was passed to his oldest son George, who later became George III.
It was handed out again in 1866 by Queen Victoria who bestowed it on her second son Prince Alfred in a move from the tradition of making a second son Duke of York.
The third person to be given it was Philip on the eve of his marriage to the then Princess Elizabeth - making her the Duchess of Edinburgh. It was granted by George VI.
When Philip died aged 99 last year, the title was passed down to his eldest son Charles but when he became King in September, the Duke of Edinburgh title merged with the Crown.
Wedding day pledge
When the Queen and Philip's youngest son Prince Edward wed Sophie Rhys-Jones in 1999, eyebrows were raised when he wasn't awarded a dukedom.
Instead, he was made Earl of Wessex, making Sophie the Countess of Wessex.
However, it was announced at the time of the nuptials that Edward would succeed his father as the Duke of Edinburgh with the blessing of his parents - making Sophie Duchess of Edinburgh.
Sophie once told the Telegraph of the moment she and Edward were told Philip would like them to take on the title.
She said: “We sat there slightly stunned. He literally came straight in and said, ‘Right. I’d like it very much if you would consider that’.”
However, Edward has previously stated how the final decision on the title rests with Charles.
Edward told the BBC : "It was fine in theory, ages ago when it was sort of a pipe dream of my father’s .... and of course, it will depend on whether or not the Prince of Wales, when he becomes King, whether he’ll do that, so we’ll wait and see.
"So yes, it will be quite a challenge taking that on.”
'Ripped up plan'
However, now Charles has ascended to the throne, there have been reports that he does not plan to honour his late parents' pledge.
It is claimed that the King, who is widely believed to favour slimming down the monarchy, is not keen on the idea.
A palace source told the Daily Mail: "The King wants to slim down the monarchy [so] it wouldn't make sense to make the Earl the Duke of Edinburgh.
"The King wants to slim down the monarchy, as is well known. That means it wouldn't make sense to make the Earl the Duke of Edinburgh.
"It's a hereditary title which would then be passed on to the Earl and Countess of Wessex's son, James, Viscount Severn.
"Essentially, this was accepted by the Earl when he agreed that his children would not be a prince or princess."
'Plan for Princess Charlotte'
Now royal insiders have claimed that the reason why Charles may withhold the title from Edward is because he wants to give the dukedom to his oldest granddaughter Charlotte.
Prince William's second child, who is third in line to the throne after her father and brother Prince George, could receive the dukedom and title - that once belonged to the Queen - as Charles wants to "honour the line of succession", according to a source.
A source told the Mail on Sunday : "Discussions are underway, but the favoured outcome for the King is that this title ought to go to Princess Charlotte.
"It would be a fitting way to remember the Queen – who, of course, had the title Duchess of Edinburgh – and a way for His Majesty to honour the line of succession."
However, when William ascends to the throne, Charlotte could instead be given the title of The Princess Royal - which Princess Anne now holds.
