Christine McPherson (Saoirse Ronan) is someone cursed with that familiar, often painful, gift of youth—absolute certainty. She feels everything strongly, expresses her opinions loudly, and both wounds and charms the people around her without meaning to. On the brink of adulthood, she’s resolute enough about her desire to go to college on the East Coast (far from her home of Sacramento) that she tosses herself out of a moving car when her mother Marion (Laurie Metcalf) tries to dismiss her ambitions. Another movie might frame that moment as frightening or foolish, but Greta Gerwig’s Lady Bird celebrates Christine’s teenage will, no matter how extreme it can sometimes be.

Christine prefers to be called “Lady Bird,” which she considers her “given name” (“I gave it to myself, it was given to me by me,” she explains). She wants to be an actress, but keeps getting small, nameless roles in the school plays; she wants to go to a university like Yale, but probably not Yale, since her grades aren’t good enough to get in. She’s constantly boiling with passions that bounce off her weary mother, a nurse, and her good-natured if passive father (Tracy Letts), an out-of-work computer programmer. She’s sure of all the exciting things she wants to do in life, but the audience knows it’ll be a few years before she’s even remotely close to figuring out how to do them. In Christine, Gerwig (who wrote and directed) has created an incredible portrait of youth—intense, sometimes callous, always emotional—in a film that’s undoubtedly among the best of the year.

Gerwig, making her solo directing debut (she previously collaborated on the 2008 mumblecore movie Nights and Weekends with Joe Swanberg), injects Lady Bird with the kind of vivacious energy that suffused the films she co-wrote with the director Noah Baumbach (Frances Ha and Mistress America). Lady Bird is frequently laugh-out-loud funny but never short on pathos. Though small in scale (and only 93 minutes long), it still manages to cram in the entirety of Christine’s senior year and beyond. The film is also a delightful paean to Sacramento, Gerwig’s hometown, distilling just how simultaneously claustrophobic and comforting the places we come from can be, especially when we’re on the verge of fleeing them.

The best thing about Christine’s mad desire to leave the West Coast and go to a school “where writers live in the woods” is that it isn’t really motivated by anything except that adolescent need to shake up one’s entire life. Her parents have their foibles (her mother is nitpicky, her father a bit of a softie) but are portrayed with sensitivity as loving people. Her Catholic school isn’t unusually oppressive or strict. Lady Bird isn’t a movie about any searing issue; it’s just a wonderful, rare character study of a young woman figuring out her identity, and all the pitfalls that follow.

Gerwig’s sense of specificity radiates through the entire film, which is set in 2002 and pays devoted attention to the music, clothing, and attitudes of that post-9/11 moment (when that teen angst might have felt particularly useless in the face of war overseas). The director’s emotional precision is apparent in the quiet class anxieties of the McPherson family. Marion, for example, takes her daughter’s desire to fly the coop perhaps too personally, and frets that she’ll never be able to afford the life she’s dreaming up for herself. “My job is to keep you realistic,” she insists. “Seems like that’s everyone’s job,” Christine replies with a sigh.

Metcalf shines as Marion, an overflowing font of love, protectiveness, and discipline whose affection for her daughter is as obvious as her frustration. Lady Bird is a powerful illustration of the temporary tenuousness of the mother-daughter bond in the later teenage years, and the surprising strength of that connection even during times of total conflict. Gerwig knows how easily children can wound their parents and vice versa, and the film’s best moments spring from those (often accidental) blow-ups. Letts, in a much more subdued role, is equally heartfelt as Christine’s father Larry, a man in the midst of an unemployment crisis that’s as wrenching as it is mundane.

But Lady Bird is undeniably Ronan’s show, and the twice-Oscar-nominated Irish actress tackles Christine’s torrents of dialogue and endless zeal with poise. Lady Bird wouldn’t work if the teenager at its center weren’t utterly lovable, and Ronan really is, making Christine’s flaws as endearing as her warmth and vulnerability. Her mistakes are all the more winning because the audience can spot trouble a mile away, as it might with her two romantic interests (Lucas Hedges as an adorable theater kid and Timothée Chalamet as a leather jacket–wearing anarchist) or her two closest friends (the sweetly dorky Beanie Feldstein and the imperiously aloof Odeya Rush). In light of last year’s The Edge of Seventeen, it seems Hollywood may finally be entering an era of smartly written, frankly told coming-of-age tales with realistic, well-rounded young women at their center (both are from female writers and directors). Lady Bird is somehow even better—it’s funny, lively, and then devastating when it needs to be, made with the kind of confidence even its heroine could only dream of.