Harper Beckham just rang in her sixth birthday with a party at Buckingham Palace fit for a princess.

On Monday, the toddler got the royal treatment, as she feted her big day at the British monarchy's headquarters with her friends—all clad in frilly dress—and IRL Princess Beatrice of York.

Parents David and Victoria Beckham, who are arguably just a shade under from British royalty themselves, took to social media to offer fans a look into the lavish bash.

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"Our little birthday princess x Kisses," the designer captioned one epic shot, which shows the 6-year-old in a shimmery light blue Cinderella-esque gown, standing in the courtyard of the palace.

Harper's proud footballer dad also took to Instagram to share a few photos from the day, including a group shot of his daughter and her five friends posing with Princess Beatrice.

"Lucky Harper meeting a real life princess at the Palace x," he wrote.

He also posted a father-daughter shot of the pair outside of the palace: "Happy Birthday to our special little young lady ...Such a special girl who brings so much joy and happiness into our lives.. Happy 6th birthday ( I can't believe your 6 already ) have the most amazing day we love you pretty lady x," he captioned the sweet shot.

Looks like a birthday party for the books!