The Carlow teen will take the lead role alongside Jude Law, Ralph Fiennes, Edward Norton and Owen Wilson in Wes Anderson's latest flick.
With so much testosterone on set, The Grand Hotel Budapest could descend into a bit of a boy's club -- but the Oscar-nominated actress will definitely be able to hold her own.
The Atonement star proved she was one of the lads last year when she appeared in Peter Weir's gritty film The Way Back.
Saoirse starred alongside Colin Farrell and Ed Harris in the epic movie.
The film followed a group of prisoners who escaped a Siberian gulag and walked across the Siberian arctic, the Gobi desert, the Himalayas, and India.
The movie will also feature Hollywood stalwarts Bill Murray and Jeff Goldblum -- both of whom are part of Anderson's usual ensemble of actors.
There will be one other female voice though.
The veteran actress, Angela Lansbury, star of Murder She Wrote, will have a supporting role.
Wes Anderson is LA's go-to Indie director, and has made a whole host of quirky films including The Life Aquatic, The Fantastic Mr Fox and Rushmore.
Shooting for The Grand Hotel Budapest will take place in Germany early next year.
The "unfriendly family film" is set in the 1920s, and Ralph Fiennes will play a disgruntled concierge at a Hungarian hotel.