No doubt exhausted after their busy three-week tour of New Zealand and Australia, the young parents are expected to celebrate their big day privately with son Prince George.
William, Kate and George arrived home to the UK at the weekend following a successful and jam-packed overseas tour, so perhaps it's not surprising if a day at home with their feet up is all the royal couple are hoping for.
Last year, they celebrated their second wedding anniversary in different places, with William, 31, serving as an RAF search and rescue pilot in Anglesey, while a then-pregnant Kate, 32, conducted an engagement at a children's hospice in Hampshire.
It's believed their first anniversary was marked with a low-key visit to their local pub.
Millions of people tuned in to watch second-in-line to the throne William and his university sweetheart Kate marry at Westminster Abbey on 29 April, 2011. They'd become engaged the previous October while on holiday in Kenya.
They welcomed their first child together, Prince George, in July 2013.
Little George's visit to New Zealand and Australia with his parents marked his first involved in public engagements, and gave the entire world a good chance to coo over his complete cuteness.
George didn't accompany his parents to every event they attended overseas, although did make a fair few appearances, including one at a children's playgroup in New Zealand where he happily played with fellow babies, explored the toys on offer and generally just made us all go, 'awww'.
And it was at that playgroup engagement that Kate's favourite photograph of George was taken. (Probably ours as well, if we're honest!) You'll know it: that adorable snap of a happy looking George cuddling into his mum's shoulder.
According to photographer Simon Woolf, the Duchess of Cambridge was handed a black and white version of the famous image just before leaving Australia and is said to have remarked on how it was her favourite picture from the tour.
Simon told People he took the photo shortly after George was woken from a nap. "He just raised his head, smiled and dropped his head back on Princess Catherine's shoulder. And I just got that shot. It was only one shot."
And what a shot it is.
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