The royal trio will be at the ceremonial start of the race at Harewood House near Leeds on 5 July as the cyclists set off on their 2,272-mile trip, which will head through the UK, Belgium and Spain before finishing in Paris on 27 July.
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Prince Harry and the Duke and Duchess of Cambridge will be at the official start of the Tour de France
William, Kate and Harry are all big supports of British cycling. They were there to cheer on Team GB's men's sprint team at the London Olympics in 2012, with the Duke and Duchess enthusiastically celebrating together as Sir Chris Hoy and his teammates won gold in a breath-taking race.
Prince William and Kate Middleton are big fans of cycling
William and Kate have even been known to jump on bikes themselves; in 2011, St James's Palace confirmed that the couple had used the rental bikes from Boris Johnson's London cycle hire scheme.
"The Duke and Duchess of Cambridge occasionally use the London cycle scheme bicycles to undertake private journeys around London," a spokesperson confirmed.
The Duke and Duchess of Cambridge and Prince Harry cheer on the men's sprint team at London 2012
Of course, Kate's brother and sister, James Middleton and Pippa Middleton are currently cycling 3,000 miles across America for charity. On Saturday, the sporty siblings and six teammates set off on the gruelling eight day journey from California to Maryland.