Prince William is honoring his wife, Princess Catherine, on her 43rd birthday, calling her "the most incredible wife and mother."

Prince William praised his wife in a message shared to social media on her Jan. 9 birthday and posted a previously unseen photo of her by one of their go-to photographers, Matt Porteous. The black and white snap was taken in Windsor last summer and shows Princess Kate smiling as she looked into the distance, hands in the pockets of her jeans.

The Prince of Wales wrote that he and the couple’s three kids — Prince George, Princess Charlotte and Prince Louis — “are so proud” of Middleton.

In the photo, Middleton traded sleek coats and heels for something more casual. She wore a dark blazer jacket rolled and cuffed at the sleeves with a crisp white button down top.

Catherine, Princess of Wales, turns 43 on Jan. 9 and received a sweet message from her husband, Prince William.

Kate Middleton, who is celebrating her 43rd birthday on Jan. 9, has proven herself to be the shiniest jewel of the British monarchy. The princess is married to Prince William, heir to the throne.

After a challenging year, Prince William has shared a moving tribute to his wife, Kate Middleton, on her 43rd birthday describing her as “the most incredible wife and mother,” alongside a new portrait.

Princess Kate is celebrating her 43rd birthday. Her husband, Prince William, honored the "most incredible wife and mother" in a new post.

Prince William praised the strength of the Princess of Wales after a turbulent year, offering a 43rd birthday wish on social media that described her as an incredible wife and mother

Kate Middleton's 43rd birthday portrait was taken by Matt Porteous in Windsor Castle last summer. She is spending the day with Prince George, Princess Charlotte and Prince Louis.