The future king is pictured smiling at the camera against the backdrop of verdant gardens at his home in Gloucestershire.
He is wearing a blue pinstripe suit, light blue tie and dotted pocket square.
A purple flower adorns his lapel.
The photo was taken in the summer, according to Clarence House.
The photographer was Hugo Burnand, who took wedding pictures for Charles and Camilla in 2005 and the Duke and Duchess of Cambridge in 2011.
Charles also asked the photographer to take the birthday image to mark his 60th year in 2008 and he has taken a previous portrait picture of the duchess.
The prince will spend his birthday attending the annual Remembrance Day Service at the Cenotaph.
He will lay a wreath on the top step of the Cenotaph on the Queen's behalf as she watches from the balcony of the Foreign, Commonwealth and Development Office building.
Charles began placing one on his mother's behalf in 2017, with the change seen as a subtle shift of head-of-state duties.
Buckingham Palace has said that the Queen will attend the annual wreath-laying service in Whitehall, which falls on November 14 this year, and honours Britain's war dead.
It comes as the 95-year-old monarch has missed several other events after being ordered to rest by royal doctors just over three weeks ago. She spent a night in hospital on October 20 undergoing preliminary tests.
On Thursday, Charles reassured a bystander about the Queen's health as he met people in Brixton.
Charles was greeted by crowds after an engagement for the Prince's Trust in south London.
One man asked him: "Prince Charles. How is your mother?"
Charles gave him an encouraging pat on the arm, and appeared to say: "She's all right, thank you."
The royal received an early birthday cake as he welcomed organisations that have been recognised by the Queen's Awards for Enterprise to a reception at Windsor Castle on Wednesday.
Jo Taylor, owner of Reach and Rescue, a company making telescopic rescue poles for emergency personnel, gave him the cake.
Ms Taylor, whose company was recognised in the innovation category, said: "The prince laughed and said, 'You've been doing your research on me', and he slipped the card into his left pocket."
Charles recently attended the Cop26 climate summit in Glasgow, where he told world leaders that "we need to put our words and commitments into practice".
Among the long-time environmentalist's own efforts to reduce his carbon footprint is eating less meat and dairy products and converting his Aston Martin to run on cheese and wine byproducts.