StarSolidStarSolidStarSolidStarSolid(4 stars)

“Nomadland” is the kind of big and big-hearted movie — featuring a central performance at once epic and fine-tuned — that reminds you of how much life one film can hold, when circumstances allow.

Those circumstances, in this case, are the essential elements of story, actor and interpreter: Here, all three fuse into a transcendent whole, inviting viewers into an experience that is simultaneously expansive and closely observed; spacious and impossibly hemmed-in; melancholy and gloriously liberated.

The emotional instrument through whom these competing and complementary impulses thrum is the magnificent Frances McDormand, who plays a widow named Fern. As “Nomadland” begins, Fern is leaving her home in Empire, Nev., where the local gypsum mine has closed. With few employment options at her disposal, she acquires a van and sets off to join the growing number of middle-aged and older Americans who, by dint of necessity or freewheeling temperament, work as seasonal migrant laborers throughout the country, in everything from Amazon fulfillment centers to random RV parks.

Based on Jessica Bruder’s 2017 nonfiction book, “Nomadland” features a cast of real-life nomads, including Bob Wells, a proselytizer for the lifestyle whose YouTube videos have become wildly popular. This mix of professional and nonprofessional players is a specialty of writer-director Chloe Zhao, who orchestrates the film’s aesthetic balance of rough-and-ready verite and classic cinematic grandeur with admirable finesse. As she did in her breakout film “The Rider,” Zhao evinces an instinctive understanding for landscapes and the people who populate them: Here, the same sweeping vistas that such auteurs as John Ford and Henry Hathaway invested with so much hegemonic bravado are no less impressive for being the backdrop for a new, far less triumphalist form of human aspiration.

Which isn’t to say that Fern’s journey is downbeat. “I’m not homeless, I’m just house-less,” she says matter-of-factly at one point. Throughout “Nomadland,” McDormand subverts narrative expectations about Fern’s motivations: She is both enigmatic and transparent as she gets on with whatever work is at hand, whether it’s harvesting beets in Nebraska or working at Wall Drug in South Dakota. (Among the unexpected draws of “Nomadland” are the friends Fern makes along the way, including irresistibly named real-life nomads Linda May and Swankie.)

Filmed in the majestic contours of widescreen westerns, McDormand holds the camera with an utterly disarming combination of self-effacement and command — the same charismatic naturalism that made her appearances on the awards circuit a few years ago for “Three Billboards Outside Ebbing, Missouri” such an exhilarating departure from the usual empty glitz.

Figuring out what makes Fern tick — and McDormand’s openness to that inquiry — provides one narrative engine to “Nomadland.” Another is what it will take to make her settle down: When she meets a quiet, sensitive fellow traveler named Dave, the temptation is palpable (after all, he’s played by David Strathairn). But most of all, this visually lush, emotionally complex journey is gratifying for its own sake, as McDormand and Zhao take the audience into a world that for many Americans is hiding in plain sight, illuminating its underlying reality of dire economic disruption without condescension or trite polemics. That tricky narrative and emotional tone is much harder than it looks, and it’s a tribute to the filmmakers that they never let their heroine succumb to self-pity or, perhaps just as annoying, you-go-girl grit. Fern is tough and self-reliant, to be sure, but never at the expense of her own softness and longing.

Filmed by Zhao’s frequent collaborator Joshua James Richards to take full advantage of the film’s spectacular geographic settings and the preternaturally expressive face of its leading lady, “Nomadland” winds up being as contradictory as its flinty, enormously sympathetic protagonist. It’s happy and sad; soaring and earthily unsentimental. Under Zhao’s assured hand, what starts as a tone poem to the idiosyncratic urges that drive us swells into an ecstatic hymn to the ties that bind us — to each other, and to the fragile, stubbornly enduring natural world we inhabit alone, together.

R. At area theaters; also available on Hulu. Contains some full nudity. 108 minutes.