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)