Bored with farm life, and anxious for some excitement, Henry Fleming sets off to join the Union troops fighting the Civil War. An inexperienced fighter, he is anxious to get into battle to prove his patriotism and courage. He swaggers to keep up his spirits waiting for battle, but when suddenly thrust into the slaughter he is overcome with blind fear and runs from the field of battle.

He is ashamed when he joins the wounded, for he has not earned their "red badge of courage" and becomes enraged when he witnesses the death of his terribly maimed friend. In a confused struggle with his own army's retreating soldiers, he is wounded but not by enemy gunfire. In an effort to redeem himself in his own eyes, he begins to fight frantically and, in the heat of battle, automatically seizes the regiment's colors in a daring charge that proves him truly courageous.

The unnamed battle in the novel has been identified as that as Chancellorsville. While considered one of the most compelling stories of warfare of all time, Stephen Crane had never seen a battle when he wrote The Red Badge of Courage in 1895.