But astute fashion fans were quick to notice the striking similarity to the beautiful cobalt blue gown that Maxima of the Netherlands wore during the festivities to mark her becoming Queen.
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The shades of the two dresses were identical, as was the material.
Both ladies paired the dramatic numbers with a cross-body sash – but while Maxima's was blue and yellow, a riband sash of the Order of the Netherlands Lion, Mathilde, 40, wore a purple sash that perfectly offset the blue hue of her gown.
Befitting of a Queen, her outfit was finished off with a tiara.
Mathilde's creation was also similar in style to the gown that Maxima wore in her official portraits as Queen. While Maxima wore claret for the occasion, once again the material and cut of the dresses were much the same.
Mathilde and King Philippe's portraits were revealed on Wednesday.
The regal shots show a confident King posing in uniform before a majestic setting of sprawling grounds.
A purple sash is draped over the new monarch's shoulder, as he looks calm and collectedly at the camera, a trace of a smile creeping into one of the photographs.
The new Queen Consort and mother of four was striking as she posed for a photo by herself, the rich blue tone of her dress set against the lush green backdrop. She wore her hair in an elegant low chic chignon.
Stunning shots of Belgium's new number one royal couple came a day after the newly crowned King and Queen of Belgium stepped out in front of their subjects for the first time as Belgium's monarchs.
Waving to the crowds of well-wishers, Philippe and Mathilde were joined by their four children , Elisabeth, who is now first in line to the Belgian throne, Gabriel, Emmanuel and Eléonore, to mark the historic occasion.