Princess Elisabeth highlights her 'power' in one-shouldered Victoria Beckham gown

For her accessories, Elisabeth added a pair of patent stiletto pumps, as well as a clutch from her mother's collection – the 'Zoey' style by Olga Berg.

For her beauty look, the princess rocked a shimmering blue eyeshadow moment and a rosy-hued lip. Her sister, Princess Eleanore, 17, matched her stylish energy in a white broderie anglaise dress while her mother, Queen Mathilde, 52, opted for a bird printed dress by Dries van Noten and a pair of killer red Natan heels.

The evening event follows Princess Elisabeth's wearing of her military uniform to attend the military and civil parade marking Belgian National Day.

Oriona Robb, celebrity fashion stylist, tells HELLO! that Princess Elisabeth's look is a masterclass in modern royal elegance. 

"The soft blue patterned dress strikes a perfect balance between youthful charm and poised sophistication," she says. "Its gentle silhouette and subtle cinching at the waist enhance her natural grace without feeling over-styled."

Meanwhile, stylist Angela Kyte adds: "It's elegant without trying too hard, and that's exactly where her style power lies."

Two looks simply did not cut it for the Belgian National Day celebrations, as earlier in the day, Elisabeth rocked two other outfits.

For the ceremony, held at the St. Michael & St. Gudula Cathedral, Elisabeth was gorgeous in green as she donned a new Natan dress in an apple hue.

The designer number featured a sheer top with a high neck, which met a full ankle-length skirt. The look was accessorised with the 'Metropolitan Insignia Clutch in Gold' by Carolina Herrera, which her mother carried during the state visit to the Czech Republic in June, and topped it off with her mother's gold Herve Van Der Straeten earrings to match her Atelier Anne Stoffels headband.

For the party in Brussels Park, the royal, who has recently completed the first year of her two-year master's degree in public policy at Harvard University, opted for a sleeveless printed denim dress by Erdem with strappy 'Portofino 105' heels by Gianvito Rossi and a pair of Giorgio Armani earrings.