In the comparison collage, an image of the young royal from the Cambridge family's 2018 Christmas card is compared to an image of a young Diana which shows that they both share a similar facial expression as they look up with a slight smile.
The image has sent royal fans into a frenzy as many flooded the comments to gush over the similarities.
One fan wrote, "She's definitely like her granny!", while another commented about how they thought that Charlotte looked more like her father but the images side-by-side to ones of Diana show an "amazing" resemblance and that Diana "would be so proud of her boys and grandchildren."
The 2018 Christmas card shows Prince William, Kate Middleton, Prince George, Princess Charlotte and Prince Louis posing on a tree.
Charlotte stands between her parents while baby Louis is held by Kate and George strikes a cheeky pose of balancing on one leg while clinging to dad William's shoulders for support.
This isn't the first time Charlotte has been compared to someone in the royal family. Previously, her appearance has been likened to that of The Queen and her own father Prince William.
A throwback photo posted by Diana's niece Lady Kitty Spencer also sent royal fans into a frenzy as many highlighted the resemblance to Charlotte.
Fans left comments such as "I thought she was Charlotte," and "Wow Princess Charlotte definitely has the Spencer genes".
Meanwhile, some fans disagreed with the image saying that Charlotte definitely looked more like The Queen or William.