The coin is legal tender but has been designed as a limited-edition collectable or gift and will not be entering general circulation, the Treasury said.
It also said the coin’s design – which features an original portrait of Philip – was approved by the duke before his death in April this year and is being launched on Armed Forces Day on Saturday.
Chancellor Rishi Sunak said: “This coin is a fitting tribute to the Duke of Edinburgh, who moved and inspired so many people around the world with his decades of service both to the nation and her majesty the Queen.
“I’m proud to unveil the coin on Armed Forces Day, considering his distinguished naval career and unwavering dedication to our monarch and to his royal duties, and it is only right that he and the Queen are depicted together on both sides of it”.
The coin will be struck by the Royal Mint and is available from its website, as well as post offices around the UK and special stockists across the Commonwealth and worldwide, the Treasury said.
The Royal Mint will also make a £50,000 donation to the Duke of Edinburgh’s Award to support its community work in the UK and internationally, it added.
The Duke of Edinburgh served as the president of the Royal Mint Advisory Committee for 47 years.
The design drawn by artist Ian Rank-Broadley was personally approved by the duke in 2008 and the coin bears the inscription “HRH The Prince Philip, Duke of Edinburgh 1921-2021”.
Anne Jessopp, chief executive of The Royal Mint, said: “Since the passing of the Duke of Edinburgh in April, many have commented that he led a life well lived.
“He was the longest serving consort in British history, and patron or president to over 750 organisations – including The Royal Mint Advisory Committee.
“The Royal Mint has marked significant Royal events for centuries and is honoured to unveil an original new coin which celebrates the life and legacy of a remarkable man.
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