They say "life begins at 40".
And indeed, it was hard to remember a time when Princess Maxima looked more elegant or full of vitality as she arrived at the birthday celebrations to mark her milestone year.
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The bubbly wife of the Prince of Orange Willem-Alexander was appropriately dressed in a flowing gown in a dusky tangerine hue.
And completing the look was a silver clutch and delicate jewellery featuring amber stone centrepieces.
Maxima was the guest of honour at a concert marking her big day, and attending were a roll call of royal guests.
Enjoying a night out without their four children were Crown Princess Mary - pretty in a pale pink gown - and Crown Prince Frederik.
Others toating Maxima included Philippe and Mathilde of Belgium, Haakon of Norway, and of course the birthday girl's mother-in-law Queen Beatrix.
In a touching speech - which brought a tear to Willem-Alexander's eye - Maxima thanked the monarch and her husband for all their love, support and guidance.
The celebration marked not only Maxima's birthday but the tenth anniversary of her arrival in the Netherlands.
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It's a little princess!