Happy Birthday Kate Middleton! See 33 Photos Of The Duchess Of Cambridge Through The Years

Pregnant with her second child, Kate Middleton arrives at the 'Action on Addiction' Autumn Gala evening in Shoreditch in October 2014.

Kate and Prince William Leaving Connect in Cubitt Street in London in November 2013.

The Duchess of Cambridge greets a little subject at The Charity Place2Be in November 2013.

Royal spots! Catherine, Duchess of Cambridge formally names the new cruise liner the 'Royal Princess', making her the ships 'godmother.'

Princess Kate visits Naomi House Children's Hospice and chats with an adorable young girl.

Royal in red! Kate visits Dumfries House in Ayrshire, Scotland on a bitter cold day to attend the opening of the Tamar Manoukin Outdoor Centre.

Sporty Princess! Kate Middleton playing basketball at the Donald Dewar Leisure Centre in Drumchapel to launch a new Scottish project for their Foundation.

Traveling like a commoner, Kate Middleton visits Baker Street tube station to mark the 150th anniversary of the London Underground.

Kate and Prince William leave the King Edward VII Hospital together when she stayed for a few days while suffering from acute morning sickness during her first pregnancy.

The Duchess doing a royal wave as she ends her visit to the Solomon Islands on the Pacific leg of their tour of the Far East.

The Duchess of Cambridge attends a reception in Kuala Lumpur during a royal visit to Southeast Asia.

Tropical Princess! Kate arrives at the Governor General's House during a Diamond Jubilee tour of the Far East at Honiara, Solomon Islands.

Kate dances with the the ladies at the Vaiku Falekaupule.

Kate Middleton receives flowers from two year old Lola Mackay - who wouldn't let go of them - during a visit to the CRI Stockton Recovery Service, in Stockton-On-Tees, north-east England. The Duchess of Cambridge became Patron of the charity Action on Addiction in January 2012, and the focus of this visit is to learn about their work with children living with parental substance misuse and addiction. The CRI-run service in Stockton is one of the charity's licensed partners.

Kate dresses in a black and pink formal dress.

The Duchess of Cambridge on Remembrance Sunday commemorating sacrifices of the armed forces held at the Cenotaph in 2012.

The Duke and Duchess of Cambridge at the Canada Day Celebration at Parliament Hill during Royal Tour 2011.

The Royal Wedding! Prince William, Duke of Cambridge and Catherine, Duchess of Cambridge in a horse drawn carriage after their ceremony in 2011.

The newlyweds on the Buckingham Palace Balcony.

While still just Prince William's girlfriend, Kate attends the Sovereign's Parade at the Royal Military Academy Sandhurst

Sandhurst, England in 2006.

The pregnant princess and her husband attend the Christmas service at St Mary Magdalene Church, Sandringham Estate, Sandringham, Norfolk, UK on the 25th December 2014.

Kate and William at Wimbledon in the Royal Box.

Kate attended The Day-Glo Roller Disco fundraiser in 2008 in a sexy pair of hot pants!

When she was just the girlfriend of Prince William, Kate was with her dragon boating crew heading off from the Quintin Boat Club in Chiswick.

Kate Middleton on her way to work in 2007 when she was Prince William's girlfriend.

Kate and Prince George visit the Nightlife display at Taronga Zoo. 

The Duke and Duchess of Cambridge present their newborn baby at the Lindo Wing, St Mary's Hospital, Paddington, London, UK, on June 23, 2013.

The Duke and Duchess of Cambridge and Prince George arrive at the Military Terminal at Wellington Airport as they begin their tour of New Zealand and Australia in Wellington, New Zealand on April 7, 2014.

Kate helps Prince George watch the Duke of Cambridge and Prince Harry play in the Jerudong Polo Trophy at Cirencester Park Polo Club, Cirencester, Gloucestershire, UK, on June 15, 2014.