But who could forget Kate's ethereal McQueen dress, the sassy AF flower girl and, erm, Princess Eugenie and Beatrice's headwear.
The duo's Philip Treacy fascinators became iconic for all the wrong reasons and seven years later, the royal sisters have discussed the matter for the first time.
Speaking in the September issue of British Vogue, Eugenie revealed that her big sister actually broke down into tears at a Buckingham Palace garden party following the fashion critique.
She explained: "There was a horrible article that had been written about Beatrice and she got really upset.
"We were just about to step out and she had a bit of a wobble and cried. I was looking after her. And then about an hour later, I had a wobble and started crying and Bea was there for me."
Hopefully this will make people think twice before rushing to judge other's sartorial choices. You keep doing you, Bea and Eugenie!
Princess Eugenie is set to marry her long-term boyfriend, Jack Brooksbank, on October 12 after the pair got engaged earlier this month in Nicaragua.
And in a surprising break with royal tradition, the couple have revealed that they'll be hosting their guests in their back garden!
The couple, who will marry in the same chapel as Harry and Meghan, will host their reception in a marquee at their house.
Kate Middleton might be missing Princess Eugenie’s wedding (but she has a VERY good reason)
A source told "Sarah and Andrew are helping to organize the evening party.
"The plan is for a marquee to be set up in the grounds and dancing late into the night.
"Eugenie and Jack are planning the whole thing but Sarah and Andrew are very involved. Sarah is bringing a very eclectic and exciting guest list to Windsor."
We love the couple for doing things their own way - we just wish we could snag an invite to the shindig...