This gritty combat drama opens on the morning of 6th June, 1944, the beginning of the Normandy Invasion, as American soldiers prepare to land on Omaha Beach. They struggle against German infantry, machine gun nests, and artillery fire. Captain John H. Miller survives the initial landing and assembles a group of soldiers to penetrate the German defenses, leading to a breakout from the beach.
In Washington, D.C, at the U.S. War Department, General George Marshall is informed that three of the four brothers of the Ryan family were killed in action and that their mother is to receive all three telegrams in the same day. He learns that the fourth son, Private First Class James Francis Ryan, is a paratrooper, and is missing in action somewhere in Normandy. Marshall, after reading Abraham Lincoln's Bixby letter, orders that Ryan be found and sent home immediately.
Three days after D-Day, Miller receives orders to find Ryan and bring him back from the front. He assembles six men from his company — Horvath, Reiben, Mellish, Caparzo, Jackson, medic Wade - and Upham, a cartographer who speaks French and German. Miller and his men move out to Neuville; there, they meet a platoon from the 101st Airborne Division, and Caparzo dies after being shot by a sniper.
Eventually, they locate a Private James Ryan, but soon learn that he is not their man. They find a member of Ryan's regiment who informs them that his drop zone was at Vierville and that his and Ryan's companies had the same rally point. Once they reach it, Miller meets a friend of Ryan's, who reveals that Ryan is defending a strategically important bridge over the Merderet River in the town of Ramelle.
On the way to Ramelle, Miller decides to neutralize a German machine gun position, despite the misgivings of his men. Wade is fatally wounded in the ensuing skirmish, but Miller prevents a surviving German from being executed and sets him free. No longer confident in Miller's leadership, Reiben declares his intention to desert the squad and the mission, prompting a confrontation with Horvath. The argument heats up until Miller defuses the situation, and Reiben decides to stay.
Upon arrival at Ramelle, Miller and the squad come upon a small group of paratroopers, one of whom is Ryan. Ryan is told of his brothers' deaths, the mission to bring him home, and that two men had been lost in the quest to find him. He is distressed at the loss of his brothers, but does not feel it is fair to go home, asking Miller to tell his mother that he intends to stay "with the only brothers [he has] left."
Miller decides to take command and defend the bridge with what little manpower and resources are available. Elements of the 2nd SS Panzer Division arrive with infantry and armor. In the ensuing battle, while inflicting heavy German casualties, most of the Americans — including Jackson, Mellish, and Horvath — are killed. While attempting to blow the bridge, Miller is shot and mortally wounded by the German prisoner set free earlier, who has returned to battle alongside the SS.
Just before a Tiger tank reaches the bridge, an American P-51 Mustang flies over and destroys it, followed by American reinforcements who rout the remaining Germans. Upham executes the German who shot Miller and allows the rest to flee.
Reiben and Ryan are with Miller as he dies and says his last words, "James... earn this. Earn it." In the present day, the elderly Ryan and his family visit the Normandy American Cemetery and Memorial. Ryan stands at Miller's grave and asks his wife to confirm that he has led a good life, that he is a "good man" and thus worthy of the sacrifice of Miller and the others. His wife replies "You are."
At this point, Ryan stands at attention and delivers a military salute towards Miller's grave.