The palace released a portrait of Kate Middleton ahead of the Duchess' 40th birthday.

The portrait is one of three that will be displayed at the National Portrait Gallery, according to the post.

In the non-color portrait, the Duchess of Cambridge sits wearing an off-the-shoulder dress with bows tied on each shoulder. Her hair is blowing off her face and is curled.

"Delighted to share a new portrait of The Duchess ahead of her 40th birthday tomorrow," the caption read.

The palace released a new portrait of Kate Middleton ahead of the Duchess' 40th birthday.

The palace released a new portrait of Kate Middleton ahead of the Duchess' 40th birthday. (Photo by Chris Jackson/Getty Images)

KATE MIDDLETON SHARES BEHIND-THE-SCENES PHOTOS FROM ‘TOGETHER AT CHRISTMAS’ PREPARATION

"This is one of three new portraits which will enter the permanent collection of the @nationalportraitgallery, of which The Duchess is Patron."

Middleton turns 40 on Jan. 9. 

The daughter of a flight attendant and a flight dispatcher, Catherine Elizabeth Middleton was born in Reading, England, on Jan. 9, 1982, and grew up with a younger sister, Pippa, and a younger brother, James.

LAHORE, PAKISTAN - OCTOBER 18: Catherine, Duchess of Cambridge visits SOS Children’s Village, a charitable organisation in the heart of the city, on October 18, 2019 in Lahore, Pakistan. (Photo by Samir Hussein/WireImage)

The portrait is one of three that will be added to the National Portrait Gallery. (Getty)

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Middleton and Prince William married in 2011 after a long relationship. The tabloids dubbed her "Waity Katie" for her patience during their courtship

"This is the woman who was the commoner who married into the royal family and who has not tripped up, not caused any embarrassment,’’ Katie Nicholl, author of "Kate: The Future Queen." "It’s not been an easy year, and yet somehow Kate seems to be a bit of a beacon in all of this.’’

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Prince William Kate Middleton

Middleton shares three children with Prince William; Prince George, Prince Louis and Princess Charlotte. (Photo by Mark Cuthbert/UK Press via Getty Images)

Middleton and William share three kids together; Prince George, Prince Louis and Princess Charlotte.

The Associated Press contributed to this report.