Could also say Natalie Portman in Leon (The Professional)
I think Robert Duvall takes the cake here. His first role was playing Boo Radley in To Kill a Mockingbird.
Chris Evans as [Jake Wyler in Not Another Teen Movie](#spoiler).
It'd be hard to beat the one-two punch of Janelle Monáe's prominent roles in *Moonlight* and *Hidden Figures* in 2016. I think she'd only made cameo guest appearances as herself or done voice work up until that point?
He was in an Australian movie the year before, but Hugh Jackman in X-Men (2000) is a pretty damn amazing start to a career.
Jamie Lee Curtis in Halloween. She did some work in tv prior to that but her first film was a masterpiece.
Lupita Nyong'o in 12 Years A Slave.
Hands down one of the best debuts of all time.
There's quite a few but ones that come to mind are:
Natalie Portman The Professional
Frances McDormand in Blood Simple
Eddie Murphy in 48 Hours
John Malkavich in Places in the Heart
Edwarn Norton in Primal Fear
Marlee Matlin in Children of a Lesser God
Matthew David McConaughey: Dazed and Confused
Well, Christoph Waltz's American debut was inglorious bastards, which he was brilliant in!
Edward Norton in Primal Fear. Won a Golden Globe and arguably should have won the Oscar. Very impressive
Daisy Ridley's big Hollywood debut was in The Force Awakens. I think she absolutely nailed it on a big stage. Also Sissy Spacek in Badlands comes to mind.
I dont know about 'Best" in terms of performance, but I can think of three notable instant ''star-making entrances" in movies. I mean scene where a virtual unknown has 'walked in" and was a 'movie star':
Micheal Keaton in Night Shift
Cameron Diaz in The Mask
Eddie Murphy in 48hrs (granted that he was pretty well known via SNL, but had no movie prior)
I'm sure there's more.
Edward Norton Primal Fear is a good example of killer debut performance though.
Warren Beatty's first film was Splendor in the Grass, which earned him a Golden Globe nomination.
Winona Ryder in Lucas, Anna Paquin in The Piano, Anna Chlumsky in My Girl, Emily Watson in Breaking the Waves
Gary Oldman as Sid Viscious in Sid & Nancy.
Not sure if this counts since she was in a film prior that was not theatrically released in the US, but definitely Saoirse Ronan. Her first Hollywood debut was in Atonement, at age 13. What a fantastic performance, and an Oscar nomination at that age (with 3 nominations at age 23!). And she keeps making great ones.
Barkhad Abdi in Captain Phillips.
Dude went from no acting at all and a cab driver to Oscar nomination.