For her 21st birthday bash that was shared with her father, Crown Prince Pavlos's 50th birthday bash at a manor in Gloucestershire, Princess Maria-Olympia of Greece wore a long-sleeved Steven Khalil gold and grey studded one piece with a longer and full train from her waist. She also wore a pair of elevated gold Gucci sneakers with red, blue yellow, and white stripes on the elevated section.

Like all the women in attendance, Maria-Olympia wore an extravagant headpiece to fit in with the theme of "revolution."

Images were splattered all across social media of the event with hashtags like #princeandrevolution and #5021revolution. Maria-Olympia's mother, Crown Princess Marie-Chantal later said they should have had a social media blackout for the party because it portrayed the family in a way that they are not. 

Those at the celebration were Prince and Princess Michael of Kent, Crown Prince Haakon and Crown Princess Mette-Marit of Norway and Queen Máxima of the Netherlands, alongside members of the Greek Royal Family. Other guests included members of the Bulgarian Royal Family, socialites and fashion designers like Valentino Garavani and Giancarlo Giammetti.

It would be a safe bet to say that safe to assume that members of the Danish and Spanish royal families were there as well as they are closely related to the Greeks.