Valentino remains the Argentine-born princess' favourite couturier for special occasions, and according to Grazia magazine that is where she will get her outfit for Tuesday, when she becomes queen consort at the enthronement of her husband, Netherlands crown prince Willem-Alexander.
The Italian stylist also designed her 2002 wedding gown, a classic ivory number with a five-metre (yard) train and hand-embroidered tulle veil for her marriage to Willem-Alexander, who succeeds his mother, Queen Beatrix.
A successful investment banker who worked with HSBC, Kleinwort Benson and Deutsche Bank, Maxima met the Dutch prince through friends when she was 28.
She is seen as typifying a new generation of European royals, more in tune with working women.
Auburn during her teenage years, now a blonde, the princess, who turns 42 next month, likes to wear the Belgian designer Edouard Vermeulen, the Netherlands' Jan Timiniau or Benito Fernandez from Argentina.
Maxima, they all say, is indubitably one of Europe's best-dressed royals, with a marked taste for the fresh and the avant-garde that never seems to go amiss.
"She's undoubtedly a woman of our times, she's active, enjoys fashion as well as her role in the family and the nation," said Vermeulen, whose Natan house is popular with Europe's royals.
"And she has this Latin charisma and amazing smile that have made her extremely popular," he told AFP. "She was born for the role."
On the royal stage style is often paramount, with each and every appearance under the looking-glass of the fashionistas also subject to the strict rules of regal etiquette.
Benito Fernandez, who designed an outfit for Maxima's 10th wedding anniversary, said he was proud to have dressed "a princess everyone is watching".
"She's modern," he added.
The couple's daughters attend a state school and Maxima does legal work for the United Nations to help set up micro-credit firms or assist migrant women.
Maxima has a taste for bright colours -- oranges and ochres, yellows and reds -- as well as floral prints.
But for everyday wear she just as often goes for classic tailored pants, fitted jackets, knee-length skirts, or run-of-the-mill jeans and white shirts -- often off the rack at Spanish high-street retailer Zara.
At high-society events such as royal weddings or official ceremonies, however, she stands out for fancy hats and waist-hugging gowns with plunging necklines and encrusted jewels and embroidery.
Such is the "Maxima effect" in the world of hats that she is the inspiration for Belgian milliner Fabienne Delvigne, who for the past 25 years has been making hats for Europe's aristocrats.
"People are always saying, 'This one must be for Maxima,'" Delvigne told AFP in a studio littered with broad-brimmed hats and racy plumed headgear made for the princess.
"It's a pleasure to design for her, we are totally her fans," she said. "She has this unique way of moving that gives the hats their own movement, as if they were dancing."
On occasions where diamond tiaras rather than hats are required the princess prefers to wear her hair up.
But Maxima's versatility is such that in September she donned a neoprene wetsuit for a charity swim in a Dutch canal where no one would have spotted her among the crowd of swimmers.