Margot Robbie attends the Oscars held at Hollywood & Highland Center on March 2, 2014 in Hollywood, California. Credit: Steve Granitz/WireImage

The Duchess went dark! Wolf of Wall Street star Margot Robbie ditched her blonde locks and debuted a new brunette hairstyle on the Oscars red carpet Sunday, Mar. 2.

Robbie, 23, wearing a bedazzled black Saint Laurent by Hedi Slimane dress with a big bow detail on the back, made a low-key entrance outside of the Dolby Theatre in L.A. The star paired her wavy chestnut locks and dress with a plum lip color.

Robbie's latest red carpet look was a sharp contrast from her ethereal Golden Globes appearance, where the then-blonde beauty stunned in a sleeveless cream silk crepe Gucci gown embroidered with crystal and emerald appliques, and complete with a high slit.

The hair transformation has been for the star's upcoming role in 2015 book-turned-film, Z for Zachariah, in which Robbie plays a 16-year-old nuclear war survivor. She will star in the sci-fi flick opposite 12 Years a Slave Best Actor Oscar nominee Chiwetel Ejiofor and Star Trek hunk Chris Pine.

An eyewitness on the red carpet told Us Weekly that Robbie gave Ejiofor "a big hug" on the red carpet at Sunday's awards show. In addition to her role in Z for Zachariah, Warner Bros. announced last month that the star has joined the cast of the live-action 3D Tarzan movie, slated to hit theaters in July 2016. Robbie will play Jane opposite Alexander Skarsgard's Tarzan.

Tell Us: what do you think of Margot's darker look?