Why Princess Eugenie's Royal Wedding outfit is causing such a stir

The most highly anticipated event of the year is finally here.

And celebrities and members of the royal family have descended on Windsor en masse, to celebrate Prince Harry and Meghan Markle's wedding day.

But there's one guest in particular that's been causing quite the stir on social media. Princess Eugenie opted for a retro, Jackie Kennedy-inspired look, and twitter users were loving her style.

We can certainly see the resemblance! Could it be a clue to the style she'll opt for at her own wedding?

Some people were disappointed her outfit wasn't as much of a statement as the one she wore to William and Catherine's nuptials in 2011.

The York daughters were also joined by Sarah Ferguson, Prince Andrew's former wife. Her appearance marks the first time that the Duchess of York has attended an official royal event for some years. She of course didn't attend the Duke and Duchess of Cambridge's wedding in 2011.

Other famous faces from all over the globe, and the rest of the British royal family have joined the happy couple to celebrate their big day - including Meghan's on-screen husband, Suits star Patrick Adams, and her close friend, tennis star Serena Williams.

Oprah was one of the first to arrive, looking fabulous.

Celebrity attendees also included Victoria and husband David Beckham, and fellow Spice Girls Emma Bunton and Geri Horner.

Meghan's close girlfriends also looked stunning as they turned out to support the bride, including her closest confidante, Jessica Mulroney. It's also rumoured that Jessica helped Meghan pick out her stunning Givenchy wedding dress.

The Queen, perhaps one of the most important guests on the day, looked as elegant as ever, in a “delicately flared dress in lime, lemon. purple and gray printed silk,” as described by British bridal designer Stewart Parvin. While Meghan Markle's mother looked picture perfect in a stunning green suit.

Of course, the couple were also joined by the Duke and Duchess of Cambridge for the wedding too. Prince William joined Harry at the altar as best man, looking sharp as ever in his military uniform.

So which were the most stylish Royal Wedding guest outfits of the day?

Amal Clooney stunned in a matching yellow hat and gown. Gorgeous George didn't stand a chance walking in with Amal - all eyes were on the activist and barrister and her effortlesslychic, mustard yellow Stella McCartney dress.

Harry's ex, Cressida Bonas opted for a pretty pinstripe dress - perfect for a summer wedding.

Pregnant Pippa Middleton and husband James make a stylish couple for the big day.Pippa opted for a long-sleevedfloral-printed mintgreen dress with a pleated pink and green skirt by Tom Ford.

Fergie looked smashing in a Philip Treacy fascinator, which matched her demure suit perfectly.