The Carlow native is lined-up to star in the film adaption of Vera Brittain’s 1933 memoir Testament of Youth.
The period drama will be produced by Harry Potter's David Heyman and heralds Ronan’s return to the genre after her action-packed role in Hanna.
The story, which has been adapted by Calendar Girls’ Juliette Towhidi, traces Brittain’s experiences as a disillusioned nurse during the war and the beginning of her career as a journalist and pacifist.
Ronan, who jumped to the top of A-list after Antonement, has several projects in the pipeline including Byzantium, The Order of the Seven and Noah.
Next year, the Lovely Bones actress will also appear in the film adaptation of Stephenie Meyer's novel The Host as Melanie Stryder, one of the many humans whose body has been inhabited by aliens from another planet.