In the late 19th century, after the murder of her father by Tom Chaney, a drifter and hired hand, 14-year-old Mattie Ross is determined to bring the killer to justice. She seeks the aid of Rooster Cogburn, a U.S. Marshal known for his toughness, drunkenness, and "true grit." Despite his initial reluctance and perceived unsavory character, Mattie insists on hiring Cogburn, believing he has the necessary experience and grit to track down Chaney, who has fled into Indian Territory.

Mattie and Cogburn are joined by Texas Ranger LaBoeuf, who has been pursuing Chaney for his own reasons, to kill a Texas senator and collect a substantial reward. The unlikely trio forms a partnership fraught with disagreements and contrasting motivations, but they are united in their quest. They embark on a perilous journey through rough terrain, braving the elements and outlaws, as Mattie's resolve is tested and she discovers the true cost and complexity of seeking vengeance.