695550813CJ421_2017_Vanity_

BEVERLY HILLS, CA - FEBRUARY 26: Actress Rooney Mara attends the 2017 Vanity Fair Oscar Party hosted by Graydon Carter at Wallis Annenberg Center for the Performing Arts on February 26, 2017 in Beverly Hills, California. (Photo by John Shearer/Getty Images)

John Shearer

Since her breakout role in The Girl With The Dragon Tattoo, Rooney Mara has quickly made a name for herself as a fashion darling, quickly defining a red carpet niche in dark, gothic-meets-romantic dresses, often by outgoing Givenchy designer Riccardo Tisci.

At Sunday night evening's Vanity Fair-hosted Oscar Party, however, Mara was completely unrecognizable, sartorially speaking. Not only was she wearing a lighter hue than usual, but it was also not a major, Paris house-designed gown. Rather, it was H&M--and for good reason. Designed exclusively for the actress, the pleated off-white gown designed by H&M Conscious was made of a georgette crafted from recycled polyester.

Kevin Mazur/Getty Images

Mara was not the only one making a sustainable fashion statement at the Academy Awards, however. Emma Roberts partnered with Red Carpet Green Dress, the fashion campaign founded by Suzy Amis Cameron, which challenges designers worldwide to create a red carpet worthy dress made of environmentally and socially responsible fabrics, on her gown for the ceremony: a Giorgio Armani gown from his very first Privé collection. Originally debuted in Paris in January 2005, the gown is embroidered with cream crystals and white jet beads and features a a two-tiered skirt and plunging neckline made of jet and black crystal teardrops. Speaking to Ryan Seacrest on the red carpet, Roberts noted she's always had a special affection for vintage gowns, and even inadvertently selected aunt Julia Roberts's famous black and white archival Valentino gown for the 2001 Academy Awards, or, as Roberts then referred to it,, "the skunk gown."

Also participating in the Red Carpet Green Dress challenge this year was Lion actress Priyanka Bose, wearing a custom Vivienne Westwood dress, crafted from fabrics used in past collections, as well as leftover sequins and reclaimed Swarovski crystals.

On the more unexpected end of sustainable fashion was Olivia Culpo in a custom Marchesa gown made of... beer glasses. In partnership with Stella Artois and Water.org, designers Georgina Chapman and Keren Craig created the piece using one-of-a-kind glass beads from Stella Artois's Limited-Edition Chalices in support of their “Buy A Lady A Drink” campaign, which helps to provide clean water for people in the developing world.

Photo by Getty Images.

The environmentally friendly looks come just a week after Emma Watson launched her fashion-centric Instagram account @the_press_tour, which highlights all of the sustainable pieces she is wearing during the promo tour of Beauty and the Beast. In each caption, Watson explains how her red carpet looks came to be--consciously, of course. For her Emilia Wickstead off-the-shoulder gown, worn to a special screening of the film in London, Watson wrote: "The gown is made from end-of-line fabric sourced from a family-run, London business specializing in couture fabrics, and produced in Italy. These unwanted fabric pieces have been given a new lease of life; often irregular quantities of surplus or end-of-line fabrics cannot be sold and are destroyed. This piece was created in Emilia Wickstead's London atelier, by an all-female team."

You can take the girl out of Hogwarts...

Rooney Mara’s Favorite Love Scene Is an Awkward Love Scene