Tate, whose 1969 death at the hands of the Manson family - headed by cult leader Charles Manson - serves as a backdrop for Tarantino's upcoming entertainment industry tale.
In the picture shared on the I, Tonya actress' Instagram page, Robbie is seen wearing a black turtleneck paired with a white mini skirt and white boots. Robbie let the photo of her scarily accurate take on Tate do the talking, keeping the caption simple: "First look".
While the late actress' family members weren't always keen on the film, given the tragic circumstances, her sister Debra Tate recently gave Tarantino their blessing after the director approached her about the project.
One thing we do know is that the fantastic cast will also include Al Pacino, Timothy Olyphant, Damian Lewis, Dakota Fanning, Emile Hirsch, Tim Roth, Michael Madsen, Scoot McNairy, Clifton Collins, Luke Perry, and Burt Reynolds.
"I've been working on this script for five years, as well as living in Los Angeles County most of my life, including in 1969, when I was seven years old", Tarantino said in a statement in February, via The Hollywood Reporter.
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Robbie took to Instagram on Monday to share the first snap of herself in character as Sharon Tate, the silver screen star who dazzled Hollywood in the 1960s, starring on series including The Beverly Hillbillies, Mister Ed, and The Man from U.N.C.L.E. and in films like Eye of the Devil, The Fearless Vampire Killers, Valley of the Dolls, and The Wrecking Crew.
DiCaprio leads Once Upon a Time in Hollywood as a struggling actor who gets caught up in a mystery surrounding the Manson murders.
The film was originally set to be released on the 50th anniversary of the Manson Murders - 9 August - but it has now been pushed back.
Once Upon a Time in Hollywood is set to hit theaters August 19, 2019.
Tate's sister Debra, who owns the rights to Sharon's story, and her family have had mixed reviews of the film so far.