The British actor will star in the biopic of Indian mathematician Srinivasa Ramanujan, to be played by Dev Patel.
Iron will portray English mathematician GH Hardy, the man who discovered Ramanujan in Edwardian India and brought him to Cambridge University.
Matthew Brown will direct the project from his own screenplay, based on the biography The Man Who Knew Infinity: A Life of the Genius Ramanujan by Robert Kanigel.
Producer Edward R Pressman said: "I am delighted to be working with Jeremy again. Our last collaboration on Reversal of Fortune earned an Oscar for Jeremy, and I could not overstate his amazing talent.
"We are very fortunate to be able to add an actor of such stature to our production."
Dev Patel currently stars in HBO's The Newsroom, and recently completed filming Child 44 and The Road Within.
Production on the film is expected to begin on locations in the UK and India next year.
Catch up on all the latest TV and Movies releases in Digital Spy's Screen Time: