On the morning of June 6, 1944, the beginning of the Normandy invasion, 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., 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 three telegrams to inform her of that. 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 must 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, and Wade, plus one man detailed from another unit, Upham, a cartographer who speaks French and German. Miller and his men move out to Neuville. On the outskirts of the town, they meet a platoon from the 101st Airborne Division. After entering the town, Caparzo is shot by a sniper. Jackson is able to kill the sniper, but Caparzo dies. They locate a Private James Frederick Ryan, but soon realize 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 locates 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. The last surviving German, known only as "Steamboat Willie", incurs the wrath of all the squad members except Upham, who protests to Miller about the proposed execution of the German soldier. "Steamboat Willie" pleads for his life and Miller decides to let him walk away, blindfolded, and surrender himself to the next Allied patrol. 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. Reiben then reluctantly decides to stay.
The squad finally arrives on the outskirts of Ramelle, where they come upon three paratroopers, among whom is Ryan. After entering Ramelle, 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. Just before a Tiger tank reaches the bridge, an American P-51 Mustang flies over and destroys it, followed by more Mustangs, American infantry, and M4 Sherman tanks who rout the remaining Germans. Upham, who was cut off and hid in a ditch, comes out of hiding as the Germans flee and orders them to drop their weapons; among them the German that shot Miller. Upham executes him, telling the rest to flee. Ryan is with Miller as he dies and says his last words, "James... earn this. Earn it."
In the present day, elderly Ryan and his family visit the Normandy American Cemetery and Memorial at Colleville-sur-mer in Normandy. Ryan stands at Miller's grave. He asks his wife to confirm that he has led a good life and that he is a "good man" and thus worthy of the sacrifice of Miller and the others. His wife replies "Yes, you are a good man".