The Prince and Princess of Wales were among the royal family members to send well-wishes to the Duchess of Edinburgh on Monday.
Taking to Instagram Stories, Prince William and Kate posted the beautiful portrait of Sophie that Buckingham Palace shared to mark her 60th birthday.
The photograph was taken by fashion and portrait photographer Christina Ebenezer at Sophie's Surrey home, Bagshot Park, which she shares with her husband, Prince Edward.
The message from the Waleses read: "Wishing The Duchess of Edinburgh a very happy 60th birthday today! [balloon and cake emojis]."
The official Instagram account for the King and Queen, and the royal family, also shared a video montage to celebrate Sophie's special day.
The images included showed the Duchess during a visit to Malta and other overseas trips last year, as well as at the Paris 2024 Paralympics and with some of her patronages, including Guide Dogs UK.
The Duchess is celebrating her birthday privately with Edward and their children, Lady Louise Windsor, 21, and James, Earl of Wessex, 17, before she resumes her public engagements on Tuesday.
"She doesn't want to make a big fuss about it," a friend told HELLO! magazine. "She doesn't see this as a big moment."
Sophie and Kate's special bond
Since marrying into the royal family in 2011, the Princess of Wales has formed a close bond with Prince William's aunt, Sophie.
The royal women are often seen chatting animatedly or sharing a giggle, including the moment when Kate was reduced to howls of laughter when Sophie took a tumble and nearly landed on her lap at Royal Ascot in 2017.
In the past year, the Duchess has been a pillar of support for William and Kate, amid the Princess of Wales's cancer treatment and Sophie's touching gestures and compassion have not gone unnoticed.
One such moment was Sophie tenderly placing her hand on Kate's shoulder in a supportive gesture as the two senior royals exited the balcony after the Remembrance Sunday service.