The photo was taken during a trying time for the couple, as Kate recently announced in a video that she had cancer.
Prince William and Duchess Kate turn 13th Monday's wedding anniversary will be accompanied by a never-before-seen photo of the couple.
The couple captioned the photo on their shared Instagram account: “13 years ago today.”
The Prince and Princess of Wales married on April 29, 2011 and hosted nearly 2,000 guests to celebrate their union.
Fans of the royal family saw the photo on Instagram, with one user writing, “Oh my god, it's so beautiful beyond words. Thank you for sharing such a beautiful photo. Happy anniversary today to His Excellency.'' .”
Another person commented on Duchess Kate's health: “Another happy anniversary!” I pray for her health and recovery every night. Since 2010, she has been a source of elegance, beauty, grace and thoughtful inspiration for me. Sending lots of love to your beautiful family.
The photo comes at a trying time for the couple, as Kate recently announced in a video that she has cancer.
“This has, of course, been a huge shock. William and I have done everything we can to handle and manage this privately for our young family,” the royal said.
“As you can imagine, this took a while. It took time to recover from major surgery and start treatment,” Kate said, referring to her abdominal surgery, which was scheduled for January.
“But most importantly, I took the time to explain everything in the proper way to George, Charlotte and Louis and reassure them that I was okay.”
The news of Duchess Kate's cancer was announced by Buckingham Palace shortly after King Charles was diagnosed with cancer on February 5th.
Neither has disclosed what type of cancer they have or how severe it is.
Prince Charles will make his first public appearance on Tuesday after taking some time off, the palace announced last week.
Read now: Royal news: Congratulations pour in for Duchess Kate amid cancer battle