The Prince of Wales shared a new picture and described his wife as 'remarkable' in a touching birthday tribute on Instagram.

Happy birthday Princess Kate! And happy new-royal-portrait-day to the rest of us. In honor of Kate Middleton ’ s 43rd birthday on January 9, Prince William shared a new black-and-white portrait of the Princess of Wales on the couple’s official Instagram, with a sweet message in the caption.

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.

In honour of Kate Middleton's 43rd birthday, William has taken to Instagram with an uncharacteristically personal message for his wife.

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

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-up top. Completing the outfit was a checked plaid printed scarf worn around the neck and fitted dark jeans with light whiskering at the hips.

Kate Middleton may have retrieved from the spotlight within the past year, but that doesn’t mean her impact hasn’t been felt by the royals. The Princess of Wales, who is celebrating her 43rd birthday Thursday,