Cillian Murphy

as J. Robert Oppenheimer

Emily Blunt

as Kitty Oppenheimer

Matt Damon

as Leslie Groves

Robert Downey Jr.

as Lewis Strauss

Florence Pugh

as Jean Tatlock

Josh Hartnett

as Ernest Lawrence

Casey Affleck

as Boris Pash

Rami Malek

as David Hill

Kenneth Branagh

as Niels Bohr

Benny Safdie

as Edward Teller

Jason Clarke

as Roger Robb

Dylan Arnold

as Frank Oppenheimer

Tom Conti

as Albert Einstein

James D'Arcy

as Patrick Blackett

David Dastmalchian

as William Borden

Dane DeHaan

as Kenneth Nichols

Alden Ehrenreich

as Senate Aide

Tony Goldwyn

as Gordon Gray

Jefferson Hall

as Haakon Chevalier

David Krumholtz

as Isidor Rabi

Matthew Modine

as Vannevar Bush

Scott Grimes

as Counsel

Kurt Koehler

as Thomas Morgan

John Gowans

as Ward Evans

Macon Blair

as Lloyd Garrison

Harry Groener

as Senator McGee

Gregory Jbara

as Chairman Magnuson

Ted King

as Senator Bartlett

Tim DeKay

as Senator Pastore

Steven Houska

as Senator Scott

Petrie Willink

as Dutch Student

Matthias Schweighöfer

as Werner Heisenberg

Alex Wolff

as Luis Alvarez

Josh Zuckerman

as Rossi Lomanitz

Rory Keane

as Hartland Snyder

Michael Angarano

as Robert Serber

Emma Dumont

as Jackie Oppenheimer

Sadie Stratton

as Mary Washburn

Britt Kyle

as Barbara Chevalier

Guy Burnet

as George Eltenton

Tom Jenkins

as Richard Tolman

Louise Lombard

as Ruth Tolman

Michael Andrew Baker

as Joe Volpe

Jeff Hephner

as Congressman

Olli Haaskivi

as Edward Condon

David Rysdahl

as Donald Hornig

Josh Peck

as Kenneth Bainbridge

Jack Quaid

as Richard Feynman

Brett DelBuono

as Concerned Scientist

Gustaf Skarsgård

as Hans Bethe

James Urbaniak

as Kurt Gödel

Trond Fausa Aurvåg

as George Kistiakowsky

Devon Bostick

as Seth Neddermeyer

Danny Deferrari

as Enrico Fermi

Christopher Denham

as Klaus Fuchs

Jessica Erin Martin

as Charlotte Serber

Ronald Auguste

as J. Ernest Wilkins

Máté Haumann

as Leo Szilard

Olivia Thirlby

as Lilli Hornig

Jack Cutmore-Scott

as Lyall Johnson

Harrison Gilbertson

as Philip Morrison

James Remar

as Henry Stimson

Will Roberts

as George C. Marshall

Pat Skipper

as James Byrnes

Steve Coulter

as James Conant

Jeremy John Wells

as AAF Officer

Sean Avery

as Weatherman

Adam Kroeger

as Army Captain

Drew Kenney

as Soldier

Bryce Johnson

as AAF Officer 2

Flora Nolan

as Burn Victim

Kerry Westcott

as Laughing Woman

Christina Hogue

as Kissing Woman

Clay Bunker

as Kissing Man

Tyler Beardsley

as Weeping Man

Maria Teresa Zuppetta

as Consoling Woman

Kate French

as Presidential Aide

Gary Oldman

as Harry Truman

Hap Lawrence

as Lyndon Johnson

Meg Schimelpfenig

as Senator's Assistant (uncredited)