Prince Philip poses with Queen Elizabeth in new photo to mark his 99th birthday

Prince Philip will turn 99 on Wednesday.

To celebrate his birthday, Buckingham Palace released a new photo of Philip posing with his wife, Queen Elizabeth II.

The photo was taken on June 1 in the quadrangle at Windsor Castle, according to Buckingham Palace.

The queen is wearing an Angela Kelly dress with the Cullinan V diamond brooch, while Philip is wearing a Household Division tie, according to the palace.

Philip and Queen Elizabeth, 94, have been staying at Windsor Castle since March, arriving earlier than usual due to the coronavirus pandemic.

ABC News understands the prince will be celebrating his birthday privately with Queen Elizabeth.

The Duke of Edinburgh received birthday wishes on social media from members of the royal family, including his oldest son, Prince Charles, and his grandson, Prince William and his wife Duchess Kate.

Prince Philip, who wed then-Princess Elizabeth in 1947, retired from official royal duties in 2017.

He had at that time completed 22,220 solo engagements since 1952, given 5,496 speeches in his travels to more than 76 countries, authored 14 books, served as patron to 785 organizations and made 637 solo overseas visits, according to Buckingham Palace.

The Duke of Edinburgh was hospitalized in London in December last year for "observation and treatment in relation to a pre-existing condition," the palace said at the time. He was released from the hospital on Christmas Eve.