Chuck Nolan (Tom Hanks) is a systems engineer for Federal Express, and the film opens with him showing their Moscow (Russia) staff how FedEx does business. The most important thing he tells them about is time: that the package sorting must be completed precisely on schedule. To prove it, he opens a package he sent to himself from his home base in Memphis, Tennessee, that contains a small timer. Chuck stops it at 87 hours, which he says is a deplorable delivery time. Later, the package sort is threatened when one of the Moscow office's trucks is booted in Red Square. The package sorting is carried out in the street.
He returns to Memphis, FedEx headquarters, and visits his girlfriend Kelly (Helen Hunt). He proposes to her on Christmas Eve and they exchange gifts. He gets a message that he needs to go to Malaysia. Dedicated to his job, he tells her "Ill be right back." He is the only passenger and rides in the jump seat of a FedEx cargo MD-11 across the Pacific Ocean.
The plane encounters a fierce storm. The pilot attempts to fly around it but for unknown reasons the plane crashes. Noland is the only survivor and is washed onto the shore of a very small tropical island. Chuck explores the island and finds a number of FedEx packages from the crash that have washed ashore. He also discovers the body of one of the aircraft's pilots. Chuck buries him. At night on the beach Chuck sees the lights of a ship. Using a small flashlight he recovered from the body of the pilot, he tries to signal the ship but is unsuccessful.
The next morning he attempts to leave the island in the rubber raft from the jet. The high breakers over the coral reef surrounding the island turn the raft over. He's tossed onto the reef and his thigh is badly lacerated. Recovering from the accident. he begins to build a simple camp and opens the FedEx parcels. He discovers several items that aid him in his survival including a pair of ice skates. Another parcel contains a volley ball that eventually becomes his companion. One of the parcels is decorated with a pair of wings and for unexplained reasons he doesn't open it. He tries to build a fire by rubbing a stick against a piece of wood, but cuts his hand. In a fury, he grabs the volley ball and throws it. His cut hand leaves a bloody imprint on the ball and from that he adds in a face, naming it by its brand name, "Wilson". The ball becomes his companion.
Chuck figures out how to start a fire and soon teaches himself to catch crabs, open coconuts, collect drinking water and spear fish. Chuck creates a rudimentary home in a small cave. Still suffering from a tooth that was bothering him before he left Memphis, it has abscessed and is extremely painful and swollen. He finally resorts to using the toe of an ice skate blade with a rock as a hammer to extract the tooth.
Sometime later he describes to Wilson the flight path of his jet compared to its last known position and calculates that the search area is over 500,000 square miles, twice the size of Texas. He realizes its doubtful that he'll ever be found.
Four years pass. Chuck has lost more than 50 pounds and his hair and beard are long and unkempt. He survives day-to-day. During a storm two of the walls of a broken fiberglass portable toilet are tossed on shore. When he sees it blown by the wind, he realizes he might be able to use it as a sail. He is suddenly energized with the idea of building a raft that will use the fiberglass walls like a makeshift sail. He chops down trees and lays out his raft. To tie the poles together, he braids rope from local tree bark and from video tape he found in one of the parcels. He counts the days necessary to catch the northeast trade winds that he hopes will take him into the shipping lanes and rescue. Chuck isn't certain where he is headed but figures that he would rather die at sea that spend the rest of his life alone on the island.
Chuck prepares food, water, and other necessities for his escape. He ties his 'companion' Wilson and the FedEx parcel decorated with wings to the raft. With the aid ofthe toilet stall walls as a sail and a pair of makeshift oars, he's able to sail over the reef surf and escape the island and lagoon. He sails for many days and during a storm, the ball named Wilson floats away while Chuck is asleep. Chuck is awakened by water in his face, apparently from the spout of a whale, and sees Wilson floating away. He tries to rescue Wilson, but afraid of losing the raft, he is forced to let Wilson go. He is despondent over losing Wilson. A storm wrecks Chuck's raft and it slowly begins to break apart. He has nearly given up hope of rescue when he is wakened by another whale's spout. He turns over to see a container ship passing close by. They signal that they've seen him.
Chuck flies home to Memphis and is the guest of honor at a large company-organized welcome reception. He learns that Kelly has married and has a daughter. Kelly intended to meet Chuck at the celebration but she is feeling very confused. Her husband, an orthodontist that did dental work on Chuck, apologizes for her absence. He tells Chuck that Kelly is having a difficult time coping with the his sudden reappearance. He asks Chuck to give her more time. Looking out of the window he sees Kelly in tears, comforted by her husband, and watches her get in a car and leave.
Later that evening, Chuck takes a taxi to Kelly's home. She seems to be expecting him and invites him inside. They talk about little things and he discovers how much her life and ambitions have changed and how she coped with his presumed death. Chuck gives Kelly back the watch she had given him telling her that it is a family heirloom and should remain in her family. She tells him that the company presumed a hazardous package caught fire and caused the crash. She shows him that his island was more than 600 miles from the Cook Islands around which the search had been conducted. He had drifted 500 miles in his raft before he was found. He decides to keep her picture. She gives him the keys to his car that she has kept. They apologize to each other for all that has happened and he drives off slowly in the pouring rain.
Kelly suddenly runs after him, shouting his name. He backs up and they embrace fiercely in the pouring rain. She tells him that she always believed he was alive, but that others said she had to move on. She tells him that he's the love of her life. He says he loves her too. They talk for a few more minutes in his car but Chuck tells Kelly that she needs to go home.
Chuck later describes the meeting with Kelly to a colleague and friend, and how he understands and accepts that while they will always love each other, their lives have gone in different directions and they cannot be together. He confesses to the utter despair and helplessness he felt on the island, describes his failed attempt at suicide, and how he received assurance that he was supposed to live and came to terms with his isolation. While he has just lost her again, he accepts it and understands he has to take live one day at a time because you never know what the tide will bring.
He drives to Texas with the FedEx package decorated with wings in his Jeep. He attempts to deliver it but no one is there. He leaves it at the door with a note stating that the parcel saved his life. He drives south and at a four-way intersection and gets out of his car to look at a map. A friendly, pretty woman in an old pick-up truck stops and asks him if he is lost. He confesses he hasn't made up his mind where he was going. She tells him where the four roads lead, and that north, the direction Chuck had just come from, leads to a whole lot of nothingness. She drives north and as she pulls away, Chuck is surprised to see the same pair of wings that were on the package on the tail gate of her truck. Chuck walks to the center of the intersection and looks in each direction for a few seconds. He then turns north and his gaze lingers in the direction the woman drove.