Who Plays Oppenheimer In The New Movie & What Made Christopher Nolan Cast Him?

While Christopher Nolan worked with Cillian Murphy on five films previous to their latest collaboration, the venerable actor is stepping into an entirely new realm with the iconic writer and director's historical epic "Oppenheimer."

Murphy stars as the titular real-life figure J. Robert Oppenheimer in "Oppenheimer," which marks the first time the actor has played the lead role in a Nolan production. The film, which opens in theaters July 21, 2023, chronicles Oppenheimer's fateful path to developing the atomic bomb during World War II and details the repercussions that happened in its wake.

While Nolan is well-familiar with Murphy's work because of their previous collaborations, the filmmaker told The Playlist that he didn't start on his work on "Oppenheimer" with Murphy in mind. In fact, Nolan noted, he doesn't picture any particular actor for his films when he's developing them. "Well, when I write, I try to be disciplined and not write with actors in mind because if you're writing with an actor in mind, you're writing about something they've already done and you're never going to challenge them," Nolan told The Playlist.

But when it came to casting the role, Nolan said, it was about the real-life way Oppenheimer gazed at things when he was alive that convinced him that Murphy was the actor he needed to fulfill his vision.

The book that inspired Christopher Nolan's "Oppenheimer" is "American Prometheus: The Triumph and Tragedy of J. Robert Oppenheimer" by authors Kai Bird and Martin Sherwin. In his interview with The Playlist, Christopher Nolan said when he's writing a story with real people like Oppenheimer at the core, he thinks of those people first as he's crafting the script. As such, it was only after he finished writing that he imagined Murphy in the role of the person who came to be known as "the father of the atomic bomb."

"I try to write, even with fiction, but especially dealing with historical figures, with real people, I try to write with those characters in mind, and in the case of 'Oppenheimer' when we finished, and there on my desk is this copy of 'American Prometheus' I've been staring at for months and months and months with this face looking up with this intense blue-eyed stern," Nolan recalled for The Playlist. "And you sort of look at it and you think, 'I know who can do that. I know who can be that person.'"

The benefit for Nolan, of course, was that his work with Murphy dated back 18 years to when his audition for the lead role in the filmmaker's "Batman Begins" in 2005 yielded a positive result in a much different way.

While the coveted role of Batman-Bruce Wayne went, of course, to Christian Bale, Christopher Nolan said Cillian Murphy created an "electric atmosphere" when he tried on the Batsuit for his "Batman Begins" audition. And while it seems on its face like Murphy missed the chance at a big opportunity, the audition instead led to Murphy landing the pivotal role of Dr. Jonathan Crane, aka the Scarecrow, one of the main villains in "Batman Begins."

From there, Murphy reprised his role as Crane in "The Dark Knight" in 2008 and "The Dark Knight Rises" in 2012. In between those two films, the actor played a key character in Nolan's mind-bending 2010 thriller "Inception." Prior to the work together in "Oppenheimer," Murphy last collaborated with Nolan in a small but pivotal role in the filmmaker's historical epic "Dunkirk" in 2017. "Oppenheimer," though, offered Murphy his biggest opportunity with Nolan yet. 

"Cillian is one of the greatest actors of his generation or any other, and I've known that for 20 years since I started working with him," Nolan told The Playlist. "But I've never had the opportunity to work with him as a lead. And in this case, I got to call him up and say, 'This is the one. This is you taking center stage. And not just that, I've written the script in the first person because I want to show you, and everybody involved with the project that we're going to see everything from Oppenheimer's point of view. You get to take the audience with you on this journey.'"

While Cillian Murphy is known to Christopher Nolan fans as a key member of the filmmaker's acting troupe, the performer has established a solid body of work with 60 screen roles to date, dating back to his debut in the 1997 film short "Quando."

Prior to his work with Nolan, Murphy played the lead in director Danny Boyle's 2002 horror thriller "28 Days Later." He followed up with roles in such notable films as "Girl with the Pearl Earring" and "Cold Mountain" — both in 2003. In 2005, Murphy starred as the lead opposite Rachel McAdams in director Wes Craven's airplane thriller "Red Eye."

Since then, Murphy has been a mainstay in both film and television, which included taking on the lead role in Steven Knight's Netflix crime drama 'Peaky Blinders," which ran for six seasons from 2013 to 2022. More recently, the actor starred opposite his "Oppenheimer" co-star, Emily Blunt, in 2020's "A Quiet Place Part II."

Nolan summed up why Murphy is an effective performer in his interview with The Playlist, and is thrilled how the actor incorporated his skills into playing J. Robert Oppenheimer. "He has that capacity for empathy that I think the greatest actors have. He has that ability to open up his heart and his mind to the audience and draw them in, so that's very much what we needed," Nolan told the publication. "And I mean, it was amazing to watch him work on set every day, but it really wasn't until I got in the edit suite and, my editor, and I, studied his work together that you saw the complexity, the subtlety of what he'd done."