Everything you’ve heard about the bear is true.

The frenzied grizzly-on-man attack in “The Revenant,” director Alejandro Gonzalez Inarritu’s brutal and beautiful gut-punch of a film, is such an explosion of ursine rage that it is both hard to watch and fascinating (how did they do that?).

And that is “The Revenant” in a nutshell — a grueling portrait of nature and man at their most unrelenting and unforgiving.

Based on a novel by Michael Punke, which was based on the real experiences of 19th-century frontiersman Hugh Glass — a man who sought retribution against his compatriots who left him to die in the wilderness after a bear mauling — the film may be easy to knock as a self-indulgent showcase for DiCaprio and his Oscar ambitions.

But that would be selling it short. Combining the awe-inspiring vistas of a John Ford Western (it was filmed in rugged western Canada, Argentina and Montana) with the blood-soaked justice of a Sam Peckinpah film, “The Revenant” is a gorgeously shot exercise in survival and revenge that’s definitely not for the squeamish.

DiCaprio is Glass, part of a group of hard-pressed fur traders somewhere in the wild, wild West. It’s a large, unruly squad of men headed by Captain Andrew Henry (Domhnall Gleeson), the fair-minded but put-upon leader. An attack by Indians slaughters many of them and sends the rest fleeing.

Expert tracker Glass leads the way, but then he runs across that bear. The rest of the group is left with the decision of carrying a nearly dead Glass, and thus slowing them down, or leaving him alone to let nature finish what the bear started.

Glass’ son, Hawk (Forrest Goodluck), whose mother is Indian, doesn’t want him left behind, but he’s not taken seriously by the group. The only reason he’s around is because of who his father is, and he is outweighed by cantankerous and scarred John Fitzgerald (a nearly unrecognizable Tom Hardy), a man who just wants to get paid and get out of there.

What no one expects is that Glass would not just survive but thrive on the thirst of payback.

It’s a riveting story, made all the more persuasive by Inarritu’s quest for realism. Much has been made of the physically demanding shoot that had many on the production quitting. According to The Hollywood Reporter, the set was called “a living hell” by one crew member.

All that effort shows onscreen. The actors look as if they really have been fighting for their lives, and DiCaprio turns in a visceral, unforgettable performance.

Celebrated cinematographer Emmanuel Lubezki (“Gravity,” “The Tree of Life”) turns the West into a series of striking tableaux that rival Ansel Adams.

Meanwhile, Inarritu has created a panoramic, foreboding natural world that’s completely the opposite of the claustrophobic, backstage theatricality of his last film, “Birdman.” Whereas that movie was all about language, much of the beauty of “The Revenant” is in the way it uses silence.

The director also deserves a nod for not making the Indians faceless, violent villains as that opening attack implies. Their back story gets filled in during the 156-minute running time and their motives become clear.

“The Revenant” is shot through with a spirituality, as when Glass stumbles across an Indian, Hikuc (Arthur Redcloud), who helps heal him.

While comparisons are inevitable to “The Hateful Eight,” this year’s other long, violent Western about people trying to kill each other, “The Revenant” lacks Quentin Tarantino’s tongue-in-cheek sensibilities — and it’s all the better for it.

Inarritu keeps it straight, simple and deadly. Just like the bear.