Prince Albert II of Monaco and his then-fiance Charlene Wittstock wave as they arrive at an Eagles concert, part of the three-day celebration that included their wedding. (Francois Mori/Associated Press)

Royal wedding season continues with a stunning announcement.

The princess wore pants.

Sitting in a powder-blue Chanel blazer and wide-legged silk trousers, so voluminous they seemed to form a lace-trimmed skirt, Charlene Wittstock offered a quiet “oui” in the baroque throne room of the princely palace of Monaco. The affirmative syllable, spoken at the Friday civil service between Prince Albert II and his new wife, transformed the South African-bred Olympian into Her Serene Highness, Princess Charlene of Monaco.

It was a swift transformation for a beauty who looked like Monaco’s princess long before.

One glance at Charlene’s stately, flaxen chignon and majestic stature, and it would seem as though she, not Prince Albert, were the offspring of the late Princess Grace of Monaco. The Oscar winner, called Grace Kelly before her own throne-room transformation, delivered the pinnacle of royal weddings when she dazzled 30 million television viewers at her 1956 nuptials to Prince Albert’s father, Prince Rainier. Her iconic Helen Rose wedding gown is said to be the most copied gown in history.

Catherine, Duchess of Cambridge, certainly studied the gown, re-creating its primary elements for her metamorphosis in Westminster Abbey. But Charlene’s wedding-day style was far less conservative than that of previous commoner-cum-royal brides.

The decree? Off with the tiara! The diamonds! The poofy skirt! Give the princess her couturier and a large dash of Monte Carlo extravagance, the kind no other country can afford in a global recession.

Indeed, opulence trumped formality at Saturday’s religious ceremony. How could tradition triumph when the Eagles gave a free public concert the night before?

The principality, once severe and formal, altered its customs for the nuptials, turning the morning matrimonial Roman Catholic Mass into an early evening service in the palace courtyard, only a few blocks from St. Nicholas Cathedral, where Prince Albert’s parents wed. The couple forewent other regal customs, too, like abstaining from smiling or having the bride wait awkwardly for the reigning prince to enter the ceremony last.

But refashioning tradition may be the princess’s prerogative, if her stately gown is an indication. Princess Charlene wore an off-white silk duchess Giorgio Armani Prive gown studded with 40,000 Swarovski crystals and 20,000 mother-of-pearl teardrops. Sophisticated and architectural, the silk duchess column style reflected Armani’s minimalist aesthetic, clinging to Charlene’s immaculate 5-foot-11 frame.

The imposing train, made of 20 meters of embroidered silk tulle, fastened at the nape and lay over the shorter train of her gown. The dress took the Giorgio Armani house over 2,500 hours to make. The princess omitted bejeweled accessories, wearing only a vintage-style diamond and pearl headpiece, barely visible under her low chignon and veil.

“Dressing Charlene is such a pleasure,” Armani said in an e-mail to The Washington Post. “She knows how to wear my creations with the nonchalance and confidence of youth. Charlene has the ideal figure to show off great dresses, because they highlight the fine curves and beautiful structure of her back and shoulders.”

Local bridal experts agreed that the column style accentuated her athletic frame. “The gown highlighted her lines through the bust and hips, but also kept with the tradition of a conservative neckline, long veil and elegant train,” said Julia Lichtman Kepniss, owner of Hitched Bridal Salon in Washington. “It was a contemporary choice. It reminded me of Carolyn Bessette Kennedy’s gown, very different from, say, Kate Middleton’s look.”

For the successor to Grace Kelly’s most iconic role, her gown was a wise deviation from princess style. The gown positions Charlene as Monaco’s newest fashion ambassador, a princess living between the couture capitals of Paris and Milan and on the border of France and Italy. Unlike Duchess Catherine, who must remain sensitive to British national pride, Monaco’s international jet set makes it possible for Charlene to build a wardrobe of European luxury designers, unhindered by the boundaries of one country.

She will never need to tone down royal extravagance. While the European economy suffers, glamour still reigns (and yachts) on the Cote d’Azur. Mon­egasques would never expect their princess to wear High Street or shop discount on principle.

Celebrity and royal guests took the opportunity to dress lavishly for the wedding. Belgium’s Princess Mathilde, who was in Washington on Tuesday, wore an Armani amethyst sheath, black fascinator and taupe gloves. Sweden’s Crown Princess Victoria wore an icy silver sequin cocktail dress, well suited for evening hours at the Monte Carlo casino. Other fashion notables — Chanel’s Karl Lagerfeld, LVMH’S Bernard Arnault and Armani — sat alongside the guests they clothed.

Fashion’s standout, already dubbed “Monaco’s Pippa,” was Charlotte Casiraghi, the daughter of Prince Albert’s elder sister, Princess Caroline of Han­o­ver. In a petal-pink, off-the-shoulder Chanel suit, she delivered the second reading at the Mass wearing a vintage-inspired headband with sheer netting that obscured her eyes.

The evening ended with a dinner and ball at Monaco’s Opera Garnier, where Europe’s princesses showcased new ball gowns and magnificent bejeweled heirlooms. But for the Monegasques, a people without a princess for almost three decades, all eyes were on their new one, who skipped the tiara and jewelry again. Charlene was royal enough without them.