And she hasn't stopped stunning us.
Nominated for her lead role in "Elizabeth," she wore an unusual, unstructured violet Dior gown designed by John Galliano, embroidered with a Garden of Eden design of flowers, vines and hummingbirds. At the time, Women's Wear Daily, still considered the bible of the fashion world, dubbed it "the most fantastic Oscar dress ever."
According to the book "Made for Each Other: Fashion and the Academy Awards," by Bronwyn Cosgrave, the Dior design was conceived at a London dinner party held months before the Oscars. The guests included Galliano, Blanchett, her husband Andrew Upton and her then-stylist Jessica Paster, at the Notting Hill home of Galliano's production manager, Michael Howell. Blanchett, who had poured through Galliano's look books, reportedly called the gown her "fashion orgasm."
But there were some slip-ups. According to Cosgrove, Jimmy Choo had made her matching heels with 40-carat diamond-studded ankle straps. But the shoes didn't fit and the night before the Oscars, fashion publicist Marilyn Heston had to race around town to get another pair dyed to match the deep purple-hued Dior gown.
In 2000, Blanchett looked exotic in a snug black gown from Jean-Paul Gaultier. The gold Indian-inspired bracelets by Cynthia Bach helped inspire the ethnic jewelry craze.
And when Blanchett was nominated for a supporting actress Oscar in 2005 for playing Katharine Hepburn in "The Aviator," she promised Valentino that she would wear his gown to the awards show.
Although actresses often say one thing and wear another, the designer's Oscar consultant, Carlos de Souza, promised Blanchett that, in return, Valentino would not dress anyone else. He even had to turn down supermodel Gisele Bündchen.
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The risk paid off: The gold Oscar statue went beautifully with her pale yellow Valentino silk taffeta gown with a burgundy sash. And her Lorraine Schwartz broach -- worn pinned at the shoulder -- set off a new red carpet accessory trend.
At this year's Oscars, Blanchett glittered in a silver one-shouldered Swarovski crystal mesh gown with tulle overlay from Armani Prive, the designer's couture line. She'd been flown on Giorgio Armani's private jet from her Louisiana movie set to Paris just in time for his couture runway show in January.
Naturally, it was pretty easy for Blanchett to find not just one, but two gowns, one each for her Screen Actors Guild and Academy Awards appearances.
So, what will she wear this year?
Blanchett, who reprises her first Oscar-nominated role in "Elizabeth: The Golden Age," has already worn an Armani couture gown to the Venice Film Festival, where she received best actress honors for her Bob Dylan-esque role in her other awards-contending film, "I'm Not There."
So Armani is a safe bet, especially if they do maternity gowns -- Blanchett is pregnant with her third child and is due in April. Click here for a look back at Cate's taste.
Elizabeth Snead writes the Dish Rag blog at TheEnvelope.com.