The Darkest Hour actor Olivia Thirlby is set to join the cast of Christopher Nolan's upcoming film Oppenheimer. It is the biopic of J Robert Oppenheimer, the theoretical physicist regarded as one of the fathers of the atom bomb.

The film is based on the Pulitzer Prize-winning book American Prometheus: The Triumph and Tragedy of J Robert Oppenheimer by Kai Bird and the late Martin J Sherwin.

The film will document the life of Manhattan Project leader J Robert Oppenheimer (essayed by Cillian Murphy), the theoretical physicist whose work on the Manhattan Project led to the creation of the atomic bomb.

Olivia Thirlby joins a star-studded ensemble that also includes Emily Blunt, Florence Pugh, Robert Downey Jr., Matt Damon, Rami Malek, Benny Safdie, Josh Hartnett, Dane DeHaan, Jack Quaid, Matthew Modine, Dylan Arnold, David Krumholtz, Alden Ehrenreich, David Dastmalchian, Olli Haaskivi, Jason Clarke, James D'Arcy, Michael Angarano, Guy Burnet, Danny Deferrari, Matthias Schweighöfer, Gary Oldman, Harrison Gilbertson, Emma Dumont, Devon Bostick, Trond Fausa, Christopher Denham and Josh Zuckerman.

Written by Nolan, Oppenheimer is backed by the filmmaker alongside Emma Thomas and Atlas Entertainment's Charles Roven. The film is expected to be released in theatres on July 21, 2023.