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

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

The Prince of Wales posted a birthday message for his wife, Catherine, Princess of Wales to social media on Thursday to celebrate her 43rd birthday.

Prince William pays tribute to ‘incredible wife’ Kate Middleton as princess turns 43 - Princess celebrating birthday at home after a challenging past 12 months

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.

Catherine, Princess of Wales, revealed last March that she had been diagnosed with an unspecified cancer and was undergoing chemotherapy.

Kate, the Princess of Wales, turns 43 on Thursday, capping what was a tumultuous year for the mother of three and wife of Prince William. Kate, who was born Jan. 9, 1982, is expected to spend her birthday privately with William and their kids -- Princes George and Louis and Princess Charlotte -- at home in Windsor,

Kate Middleton is celebrating her 43rd birthday and "looking after herself" after completing chemotherapy treatment, a family friend tells PEOPLE.

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.

Happy Birthday, Princess Kate! Express.co.uk shares pictures of 11 of the royal's iconic moments over the years.