The Duke shared his loving words with the couple's 9.2million followers alongside a handsome photo of Meghan, which was taken past year at the Queen's Commonwealth Canopy in Tonga.
"One of the things they said during pregnancy was "I feel the embryonic kicking of feminism".
"Meghan made it very clear that she was on a mission to make her mark and ensure that she was the duchess who everyone looked up to and admired, even if it means ruffling some more feathers", the source said.
Here are some of her top moments since her last birthday.
"Despite the fact that if you go up to someone and say, "What you've just said, or the way that you've behaved, is racist" - they'll turn around and say, 'I'm not a racist'". The Duke and Duchess of Sussex attended the film which stars Beyoncé as the voice of Nala.
Beyoncé and Jay-Z had previously shown their admiration for Meghan when they posed in front of a portrait of the Duchess of Sussex wearing a crown as they accepted a Brit award for best global group.
Many accused Markle of throwing shade at Middleton when she turned down Vogue's cover photo offer.
In 2019, she celebrated her first wedding anniversary with Prince Harry, the royal couple welcomed their first baby together Archie Harrison and the new mom has had the opportunity to work on important projects, including her guest editing gig for the September issue of British Vogue.
The issue included a conversation between Meghan and former US First Lady Michelle Obama.
There were also rumours that the Sussex clan could be joining the Queen and Prince Philip at the royal estate in Balmoral, where the Queen spends the majority of her summer days.