Princess Alexandra of Hanover and Ben Sylvester-Strautmann

Alexandra of Hanover, a Disney princess in a vibrant dress and a 492-diamonds necklace at the Rose Ball

Princess Caroline of Monaco’s youngest daughter, along with Beatrice Borromeo and Tatiana Santo Domingo, stood out as the most vibrant guests of the Principality’s big night.

MARCH 31, 2025 11:29 PM EDTMAR 31, 2025, 11:29 PM EDT

The 2025 Rose Ball didn’t disappoint. The Grimaldi family dazzled at the Salle des Étoiles in the Sporting Monte-Carlo, showcasing some of their most stunning appearances to date. Caroline of Monaco stayed true to her signature elegance in a white gown, accented with a vintage brooch. Charlotte Casiraghi went for classic black, while Alexandra of Hanover, Beatrice Borromeo, and Tatiana Santo Domingo brought a bold splash of color to the night.

Princess Caroline's son Pierre Casiraghi did not join his family at the 2025 Rose Ball

Alexandra of Hanover’s pink gown

The youngest daughter of Caroline of Monaco—and Charlotte Casiraghi’s sister—has clearly inherited her mother’s love for fashion. Staying true to her family’s signature style, the 25-year-old royal chose a bubblegum pink, Disney princess-style gown for the evening.

Princess Alexandra of Hanover attends the Rose Ball 2025 on March 29, 2025 in Monaco, Monaco. (Photo by David Nivere/SC Pool - Corbis/Getty Images)

Alexandra, who attended with her boyfriend, German-born Ben-Sylvester Strautmann, wore a V-neck dress with draped sleeves that fell softly over her arms, a corset-style bodice with fine pleating, and a flared skirt. From Giambattista Valli’s Spring-Summer 2025 Haute Couture collection (one of her favorite designers), the gown also featured delicate, hand-crafted floral embellishments at the hips—details that made it one of her most striking looks yet at the Rose Ball.

MONACO, MONACO - MARCH 29: (EDITOR'S NOTE : NO TABLOIDS WEB & PRINT, NO DAILY MAIL, NO DAILY MAIL GROUP, NO BILD, NO CHI, NO VOICI, NO CLOSER) Princess Caroline of Hanover, Princess Alexandra of Hanover and Ben Sylvester-Strautmann attend the Rose Ball 2025 on March 29, 2025 in Monaco, Monaco. (Photo by David Niviere/PLS Pool/Getty Images)

She completed the outfit with a showstopping necklace from Cartier’s Pluie collection: 492 brilliant-cut diamonds set in white gold, valued at around $383,000.

MONACO, MONACO - MARCH 29: (EDITOR'S NOTE : NO TABLOIDS WEB & PRINT, NO DAILY MAIL, NO DAILY MAIL GROUP, NO BILD, NO CHI, NO VOICI, NO CLOSER) Princess Alexandra of Hanover attends the Rose Ball 2025 on March 29, 2025 in Monaco, Monaco. (Photo by David Niviere/PLS Pool/Getty Images)

Beatrice Borromeo’s red cape dress

Pierre Casiraghi's wife, Beatrice Borromeo, also made color the focal point of her ensemble. She opted for a striking blood-red gown with a V-neckline, a pleated bodice flowing into an elegant cape, and a sheer floor-length skirt.

Beatrice Borromeo looked stunning at the Rose Ball in Monaco

To trace the dress, you’d have to go back to January 20, 2020—it's from Dior’s Spring/Summer 2020 Haute Couture collection shown in Paris.

Metallic shine for Tatiana Santo Domingo

Andrea Casiraghi and his wife Tatiana Santo Domingo

Tatiana Santo Domingo, wife of Andrea Casiraghi—Caroline of Monaco’s eldest son—joined the colorful Caribbean-themed night in a striking coral metallic dress with a hint of fuchsia.

The Colombian-American designer wore a piece by British label Erdem (€3,495), made from jacquard fabric with a linen blend and a carnation print. The dress had an asymmetric, draped silhouette and featured a bold, oversized bow on the left shoulder.