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Cynthia Erivo wears a Versace white ballgown with one diagonal strap and a thigh-high slit.
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Detail shot on Erivo's nails.
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Natalie Portman, in Dior Haute Couture, has a cape embroidered with names of women in the industry, "who were not represented for their incredible work this year." Names include Scafaria, Wang, Gerwig, Diop, Heller, Matsoukas, Ha'rel and Sciamma.
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Detail on Portman's cape.
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Charlize Theron wears chic custom made Dior gown with thigh-high slit and a single shoulder.
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Billy Porter looks like royalty in a glistening gold gown featuring a sleeveless bodice with gold feathers and a floor-length skirt in a rich baroque-style print. The ensemble was inspired by Kensington Palace and designed by British designer Giles Deacon.
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Billie Eilish walks the red carpet in a white-on-white houndstooth set, with a jacket featuring the Chanel's interlocking "C" logo. The singer is also sporting lace fingerless gloves with layered rings and necklaces, crystal accents on her nails and a messy hairdo in her signature two-tone color palette of lime green and black.
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Detail of Billie Eilish's nails.
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More regal vibes come courtesy of Olivia Colman, who's arrived on the red carpet wearing a midnight blue form-fitting gown with puffy teardrop-shaped sleeves and a cape. The actress was among the first presenters announced for the 2020 Oscars.
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"Booksmart" Kaitlyn Dever is wearing a "completely sustainable" Louis Vuitton dress made with the eco-friendly fiber Tencel.
Mike Blake/Reuters
The shiniest dress on the red carpet? Janelle Monae attends the Oscars in a glittering silver-hooded dress. The gown is by Ralph Lauren, and apparently took 600 hours to make.
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Director and Oscar-winner Spike Lee arrives in a touching Kobe Bryant tribute tux. The purple outfit shows the late basketball player's number, 24, embroidered on the lapels.
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Laura Dern looks glamorous in a pink gown with black bustier custom made by Armani Prive.
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Sandra Oh wears a dreamy pale pink sequin number by Elie Saab embellished with giant puffy tulle sleeves and skirt.
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Costume designer Sandy Powell wears the same two-piece suit she donned at the BAFTAs, continuing her effort to collect signatures -- over 100 so far -- from A-list celebrities to transform the outfit into a piece of art. Powell plans to auction the outfit through the Art Fund charity to raise money to purchase and maintain Prospect Cottage, the home of her late friend and mentor Derek Jarman.
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Best Actress nominee Saoirse Ronan is in a custom Gucci gown featuring a V-neck bodice made of the black satin left over from her BAFTAs gown, with a ruffled waist detailing. The bottom of the dress is a pale lilac skirt.
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In January, Joaquin Phoenix announced that he would wear only one Stella McCartney tuxedo on the 2020 awards red carpet to promote sustainable fashion. He's kept his word. Tonight he's appeared dressed in the same plain black tux (which he also wore to the BAFTAs, the Golden Globes and to the SAG Awards).
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Rooney is dressed in a custom cascading black lace gown by Alexander McQueen, with cutout semi-sheer lace bodice and structured puff shoulders.
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Timothée Chalamet wears a hybrid blue tracksuit-suit by Prada.
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Renée Zellweger steps on the red carpet in a custom Armani Privé one-shoulder column gown in white silk, with an open asymmetrical neckline.
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For her very first Oscars appearance, Florence Pugh has chosen a teal satin dress. Pugh is a first-time Oscar nominee for her role as Amy March in Greta Gerwig's Little Women.
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Scarlet Johansson steps onto the red carpet in an Oscar de la Renta gown with embellishments of stringed gems over a partly sheer bodice.
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Dressed in an all-black Ermenegildo Zegna tux, Mahershala Ali walks with wife Amatus Sami-Karim, who stole the show in a lavender ruffled dress.
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Brie Larson wears a metallic champagne-colored caped gown by Celine.
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Margot Robbie, who has a nomination for Best Supporting Actress for her role in "Bombshell," stepped out in a vintage strapless navy Chanel dress with a jewel pendant and cuff sleeves.
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"Once Upon a Time in Hollywood" star, Julia Butters, wore a bubblegum-pink gown by Christian Siriano, consisting of a glitter ruffled button-up top with matching pants and a skirt attached to the back.
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Maya Rudolph lights up the red carpet in a copper, sequin-covered Valentino cape dress.
CNN  — 

In one of the year’s most anticipated nights of fashion, the Oscars came alive with refined haute couture and pared-back Hollywood glamour Sunday night.

And while many of the year’s bolder fashion trends (bright green and orange ensembles) didn’t quite make their way onto the traditionally restrained red carpet at the Dolby Theater, a number of stars did use the occasion to show off statement sleeves and promote messages around sustainability.

Margot Robbie impressed with cuff sleeves that were completely detached from her strapless navy Chanel dress, while Sandra Oh’s dreamy pale pink sequin number by Elie Saab was embellished with shoulders made from giant puffy tulle. “Once Upon a Time in Hollywood” star, Julia Butters, also got in on the trend with structural shoulders on her bubblegum-pink gown by Christian Siriano.

Jordan Strauss/Invision/AP
There were various shades of pink on display, from Regina King's pale pink Versace gown (pictured) to the brighter shades worn by Idina Menzel and "Parasite" actress Park So-Dam.

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Syrian director Waad al-Kateab wears a message embroidered in Arabic on her gown

Capes were also a recurring theme, and were embraced by stars Olivia Colman and Janelle Monae. The most talked-about, however, was Natalie Portman’s Dior Haute Couture cape, which had been embroidered with names of women in the industry – including those of female directors snubbed at this year’s awards. Names included Wang (Lulu Wang of “The Farewell”), Gerwig (Greta Gerwig of “Little Women”), and Scafaria (Lorene Scarfaria of “Hustlers.”)

Similarly, Syrian filmmaker Waad al-Kateab, whose documentary “For Sama,” about the siege of Aleppo, was nominated for Best Documentary Feature, wore a pink gown with the words “We dared to dream” and “We don’t regret asking for our dignity” embroidered in Arabic.

01:19 - Source: CNN
A brief history of the red carpet

Sustainability was the other serious issue addressed on the red carpet. As expected, Joaquin Phoenix arrived in the same Stella McCartney tuxedo he’s worn throughout the awards season in his commendable stand against textile waste. And there were a number of others who used their moment in the limelight to promote more eco-friendly practices in an industry (fashion, rather than movies) that accounts for 10% of the world’s carbon emissions.

Among them was “Booksmart” star Kaitlyn Dever, who wore a Louis Vuitton dress made with the eco-friendly fiber, Tencel. Saoirse Ronan’s custom Gucci gown featured a V-neck bodice made from black satin left over from the dress she wore to last weekend’s BAFTA Awards.

Amy Sussman/Getty Images
Saoirse Ronan's dress was partly made using fabric left over from the gown she wore to the BAFTAs last weekend.

Elsewhere, there were plenty of off-the-shoulder gowns and all the expected throwback to Hollywood glamour, including Charlize Theron, who stunned in a chic custom Dior gown with thigh-high slit and a single shoulder.

Others to pull off classic looks were Renée Zellweger in a custom Armani Privé one-shoulder column gown, and, sporting a similar shade, Cynthia Erivo in a Versace ball gown with a embellished diagonal strap.

Amy Sussman/Getty Images
Charlize Theron opted for a classic look in a custom single-shoulder Dior gown with thigh-high slit.

On the menswear front, however, it was a disappointingly unadventurous night. This awards season has, thus far, been rich with colored and patterned suits, experimental headwear and gender-fluid fashion, but many of the evening’s stars stuck with the tried-and-true black-tie formula.

Attendees who have ventured into more daring territory at this year’s red carpets, such as the usually colorful Taika Waititi and Billie Eilish’s brother and producer Finneas O’Connell, kept things simple this time around in dark tailored tuxedos.

Even Timothée Chalamet, known for his flamboyant award ceremony looks, took a subdued approach in a hybrid blue Prada tracksuit-suit. His outfit quickly drew online comparisons to various professional uniforms – from paramedic to parking valet – with his red carpet photo-bomb of Margot Robbie generating more buzz than his choice of clothes.

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Timothée Chalamet took an uncharacteristically low-key approach to the red carpet.

Some attendees managed to make demure tones work in their favor, including Mahershala Ali in an all-black Ermenegildo Zegna tux, while director Spike Lee offered a rare splash of color as he paid tribute to Kobe Bryant in a purple-and-gold Gucci suit marked with the late basketball star’s jersey number.

And you can always rely on Billy Porter to bring some glamour to even the most conservative of red carpets. The “Pose” star looked like an Oscar trophy himself in a glistening gold Giles Deacon gown with sleeveless bodice, gold feathers and a floor-length skirt in a rich baroque-style print.

Scroll through the gallery for some of the night’s most memorable looks.

CNN’s Oscar Holland, Stephy Chung, Marianna Cerini and Rebecca Wright contributed to this report.