Prince Philip, who celebrates his birthday on Wednesday, has been shielding with the Queen at Windsor Castle during the coronavirus lockdown.
The photo was taken in the castle’s grounds during sunny weather last week.
It is the first public photo of the duke since he was seen leaving hospital in London on 24 December last year.
Prince Philip spent four nights in the private King Edward VII’s Hospital in relation to a “pre-existing condition”.
In the picture, which was taken by a Press Association photographer, the duke is wearing a Household Division tie.
The Queen is wearing a heart-shaped 18.8 carat diamond brooch called Cullinan V, which she has worn many times, including for her granddaughter Princess Eugenie’s wedding and London Fashion Week.
It follows another photograph last week that showed the Queen, 94, riding a pony called Balmoral Fern in Windsor Home Park.
Prince Philip, who has been married to the Queen for 72 years, has rarely been seen in public since he retired from royal duties in 2017.
He is the longest-serving consort in British history and the oldest serving partner of a reigning monarch.
The duke issued a rare statement in April thanking key workers who were keeping essential services running during the pandemic.