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, England.

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.

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

Happy birthday, Kate Middleton! Inside the Princess of Wales' plans with Prince William, Prince George, Princess Charlotte and Prince Louis.

Prince William made rare personal comments about his wife Kate Middleton in honor of her 43rd birthday. See the sweet tribute to the Princess of Wales.

Since she became the Princess of Wales, Kate Middleton has worn playful pantsuits and a plethora of polka dots.

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

Kate Middleton is celebrating her 43rd birthday by putting herself first. Less than one year after revealing her cancer diagnosis, the Princess of Wales is finding the balance between her health and work.