In June 1995, despite a lack of hiking experience, recent divorcée Cheryl Strayed (Reese Witherspoon) leaves Minneapolis, Minnesota, to hike 1,100 miles (1,800 km) of the 2,650-mile (4,260 km) Pacific Crest Trail on a journey of self-discovery and healing. During the hike, Strayed reflects in flashbacks on her childhood in Minnesota and memories of her mother, Bobbi Grey (Laura Dern). Bobbi's death from cancer sent Cheryl into a deep depression that she tried to numb with heroin and anonymous sex, which eventually destroyed her marriage to her husband Paul (Thomas Sadoski). After finding out she was pregnant, Strayed got an abortion and resolved to hike the trail to redeem herself.
Strayed begins her trek in the Mojave Desert in Southern California with her backpack. On the first night, she discovers she has brought the wrong type of gas for her stove and is therefore unable to cook food. After a few more days, Strayed meets Frank (W. Earl Brown), a farmer and construction worker who takes her in for the night and with his wife offers her a home-cooked meal and a warm shower.
Strayed meets a hiker named Greg (Kevin Rankin) who agrees to meet her at Kennedy Meadows, California. Upon arrival, she meets a camper named Ed (Cliff DeYoung) who helps Strayed strategically lighten her overweight backpack and convinces her to replace her undersized hiking boots with a new pair, to be delivered to a future stop on the trail. Strayed continues her hike into the Sierra Nevada despite Greg's warnings of deep snowfall. After removing a boot to remove a loose toenail, the boot accidentally falls down an inaccessibly deep slope, forcing her to continue the journey wearing sandals reinforced with duct tape.
Strayed's best friend Aimee (Gaby Hoffmann) sends her provisions to stops along the trail, including letters that congratulate her on her progress. Strayed also receives letters from her ex-husband Paul along the way.
On the morning of Day 58, Strayed is out of water and desperately licks the dew off her tent. Dehydrated and near exhaustion, she siphons water from a muddy puddle. While she waits for her water to disinfect, two hunters approach, one making suggestive remarks that leave Strayed feeling threatened and vulnerable. This causes her to quickly leave and run away.
Strayed makes her way out of California and arrives in Ashland, Oregon, where she meets a man named Jonathan (Michiel Huisman), with whom she attends a tribute concert to Jerry Garcia and later spends the night. Days later, Strayed arrives at Mount Hood National Forest and encounters a friendly group of young hikers who share their experiences. The hikers recognize her from the signatures she's been leaving in the hiker's record books along the PCT. Strayed frequently leaves quotes or poems that are meaningful to her along her journey.
One rainy day, Strayed finds a llama that escaped from a young boy hiking with his grandmother (Anne Gee Byrd). Strayed chats with the boy, who asks her about her parents. After she mentions her mother's death, the boy sings "Red River Valley" to Strayed, saying it is a song his mother used to sing to him. After the boy and his grandmother carry on down the trail, Strayed breaks down and cries.
On September 15, after hiking for 94 days, Strayed reaches the Bridge of the Gods on the Columbia River between Oregon and Washington, ending her journey. At various points along the trail, including at the end of the bridge, Strayed encounters a red fox, which she interprets as carrying the spirit of her mother watching over her. She reflects that, four years in the future, she will remarry at a spot in view of the bridge, five years after that have a son and one year after that have a daughter named Bobbi, after Strayed's mother.
Reese Witherspoon as Cheryl Strayed
Bobbi Lindstrom as Young Cheryl (the real-life daughter of Cheryl Strayed)
Laura Dern as Bobbi Grey, Cheryl's mother
Thomas Sadoski as Paul, Cheryl's ex-husband (based on Cheryl's ex-husband Marco Littig)
Keene McRae as Leif, Cheryl's brother
Michiel Huisman as Jonathan, a man Cheryl has sex with after meeting him in Ashland, Oregon
W. Earl Brown as Frank, a construction worker whom Cheryl asks for food
Jan Hoag as Annette, wife of Frank who serves Cheryl dinner
Gaby Hoffmann as Aimee, Cheryl's best friend in Minnesota
Kevin Rankin as Greg, a hiker Cheryl meets on the trail who ends up quitting (based on Roger Carpenter)
Brian Van Holt as the ranger in Mount Hood National Forest who opens the store for Cheryl after it was closed
Cliff DeYoung as Ed, a man at Kennedy Meadows trail stop who helps Cheryl
Mo McRae as Jimmy Carter, a reporter who interviews Cheryl for the "Hobo Times" (he mistakes her for a hobo drifter despite her denial)
Charles Baker as TJ, one of two threatening hunters Cheryl meets on the trail
Jason Newell as Ronald Nylund, Cheryl's father
Ray Buckley as Joe, Cheryl's drug-addicted boyfriend who got her pregnant resulting in an abortion
Cathryn de Prume as Stacy Johnson, a female hiker Cheryl meets on the trail
Evan O'Toole as Kyle, a young boy Cheryl meets on the trail
Anne Gee Byrd as Vera, Kyle's grandmother
Randy Schulman as Cheryl's therapist
Anne Sorce as Bobbi's nurse in the hospital
Matt Pascua as Wayne, Leif's friend
Art Alexakis as the tattoo artist
Cheryl Strayed makes an appearance at the beginning as the woman who drops off Reese at the motel.