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

Ronan, 21, received an Oscar nomination at 13 for her work in the British drama, “Atonement.” Her “Brooklyn” performance has made her an early prospect for honors in the 2015-2016 awards season.

In “Brooklyn,” Ronan displays focused, sensitive aplomb as leading lady Eilis Lacey. An economical actress, she’s especially skilled at expressing a complex 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 emotions with sensitive yet unsentimental care.

As the early 1950s-set story begins, Ronan’s unassuming Eilis lives in the small town of Enniscorthy, County Wexford. She shares a house on a grim 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 her hometown. On Sundays, she 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 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 shows Eilis’ lowly place in Ireland. It’s there that the rugby boy who 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 won’t be easy. “Brooklyn” inspires tears. First, there’s the wrenching farewell at the dock. And then in Brooklyn, Eilis’ tears fall on cherished letters from home. But she is resilient. Ronan takes the homesick Irish girl on a journey of unimagined fulfillment.

A colorful collection of supporting characters move smoothly in and out of Eilis’ story. There’s her benefactor, Jim Broadbent’s Father Flood, a kindly Irish priest in Brooklyn. Julie Walters rules the dining room table as Mrs. Kehoe, the tickleously 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. In the Brooklyn night, his affection for Eilis glows.

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