In the beautifully staged immigrant drama “Brooklyn,” Ireland’s Saoirse Ronan emerges as one of her generation’s finest actresses.

In “Brooklyn,” Ronan (who already has an Oscar nomination under her belt) displays focused, sensitive aplomb in the leading role of Eilis Lacey. An economical actress, she’s skilled at expressing a heady mix of thoughts and emotions through a silent expression or quick glance.

Ronan’s quietly commanding performance as Eilis appears in an exceptionally good literary adaptation. Nick Hornby (“Wild,” “An Education”) shaped the “Brooklyn” script from Irish author Colm Tóibín’s beloved 2009 novel of the same name. Director John Crowley (“Boy A,” “True Detective”), also Irish, handles the story’s bountiful emotion with sensitive yet unsentimental care.

As the early 1950s-set story begins, Ronan’s unassuming Eilis lives in the small town of Enniscorthy. She shares a house on a grim, gray street with her older sister, Rose, and their widowed mother.

Fiona Glascott plays Rose, the loving older sister who, realizing there’s no future for her sister in Ireland, arranges Eilis’ passage to America. In the era before widespread air travel, Rose does a brave, unselfish thing. It means the sisters will probably never see each other again.

Before Eilis boards a ship for New York, “Brooklyn” offers a telling introduction to Enniscorthy. On Sundays, Eilis works for the mean-spirited woman who runs the town grocery store. Cruel and judgmental, “Nettles” Kelly (Brid Brennan) insults and cheats her customers. Kelly also does her manipulative best to psychologically wound the good-hearted Eilis.

And there are the town’s well-to-do “rugby boys.” Sporting their blue blazers and greased-back hair, they normally wouldn’t give lower-class Eilis anything more than a dismissive glance.

On the way to a dance in Enniscorthy, where the rugby boys will be, Eilis tells her best friend, Nancy (Eileen O’Higgins), that she is going to America. The dance illustrates Eilis’ lowly place in Ireland. It’s there that the rugby boy Nancy hopes will ask her to dance actually does indeed invite her. Eilis smiles, happy that her friend got her wish. And then Eilis realizes that she is left standing alone. No one invites her to dance. Ronan, without a word, projects Eilis’ bruised pride and anger with penetrating clarity.

The snobbish rugby boys are a bit like Ireland itself. As much as they believe Eilis means nothing to them, it’s them who have nothing for her.

But leaving Ireland won’t be easy. “Brooklyn” inspires tears. First, there’s the wrenching farewell at the dock. And then in Brooklyn, Eilis’ tears fall on the cherished letters from home. But she is resilient. Ronan takes the homesick Irish girl on a journey of self-discovery and unimagined fulfillment.

A colorful collection of supporting characters move smoothly in and out of Eilis’ story. There’s Eilis’ benefactor in Brooklyn, Jim Broadbent’s kindly Irish priest, Father Flood. Julie Walters rules the dinning room table as Mrs. Kehoe, the frank and funny owner of the Brooklyn boarding house where Eilis and other Irish girls stay.

Of course, the actor playing Eilis’ Italian-American boyfriend in “Brooklyn” must be a good match for the film’s good and decent Irish girl. Emory Cohen, as Tony Fiorello, portrays this essential character with gentle, sweet tones and the sincerest of eyes.

The Irish girl and the Italian boy make a beautiful love story. But “Brooklyn” is most of all Eilis’ epic of the heart.