Princess Mary of Denmark attended the Buckingham Palace event with her husband Prince Frederik, and looked the picture of elegance in a one-shouldered gown in midnight blue velvet.
Crown Princess Mette-Marit of Norway looked equally glamorous in a sparkling silver brocade floor length gown.
She completed the look with a pair of elegant drop earrings and a simple gold bracelet.
Prince Charles and Camilla, Duchess of Cornwall, also put their best foot forward.
Getty's photographer Chris Jackson released a photo of Charles and Camilla inside the big bash.
The couple looked glam as they smiled energetically.
"On his 70th Birthday The Prince of Wales poses for a photograph with the Duchess of Cornwall before heading to his birthday party at Buckingham Palace tonight," Jackson wrote.
We're dying to know what both Kate and Meghan wore for the big event!