The Duke and Duchess of Cambridge have shared a new photo of Prince Louis to mark his third birthday.

Prince Louis turns three today (April 23), and the snap was released yesterday ahead of the young royal's big day.

The snap was taken by The Duchess of Cambridge and shows her youngest child moments before leaving for his first day of nursery school.

It was posted by the official Twitter account of the royal couple with the caption: "Three tomorrow! Taken earlier this week by The Duchess before he left for his first day of nursery, The Duke and Duchess are pleased to share a new image of Prince Louis."

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In the sweet photo, the toddler is seen wearing a blue sweater over a stripy shirt. He also dons a pair of shorts and a navy blue backpack. The grinning three-year-old sits on a red bike, gripping the handlebars as though he is ready to ride off.

Prince Louis started at Willcocks Nursery School in Kensington this week, which is the same nursery that his five-year-old sister Princess Charlotte went to before attending Thomas's Battersea, per Sky News.

Prince George went to nursery at King's Lynn.

The birthday snap comes more than a week after the official Twitter account of The Royal Family shared a photo featuring the Queen, the late Duke of Edinburgh, and their great-grandchildren. In the picture, Her Majesty can be seen holding baby Louis.

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Prince George is pictured beside his great grandmother and Princess Charlotte, who is sitting between the Queen and Prince Philip, waves at the camera.

The photo is captioned: "The Queen and The Duke of Edinburgh surrounded by seven of their great-grandchildren at Balmoral Castle in 2018."

Prince Louis is Prince William and Kate Middleton's youngest child and is fifth in line to the throne. He was born on St George’s Day, April 23, 2018, at the private Lindo Wing of St Mary’s Hospital in Paddington in London, weighing 8lb 7oz.

The Duchess of Cambridge typically releases a new photograph of each of her children on their respective birthdays.

Featured image credit: Paul Marriott / Alamy Stock Photo

Prince William and Kate Middleton release new photo of Prince Louis to celebrate third birthday