The unnamed woman in Ray Bradbury's Fahrenheit 451 holds significant importance to the novel and its main character, Montag. When the firemen arrive at the old woman's house, Montag had just questioned the function of the fire department wondering aloud if they had ever prevented fires, or if they only set them.
At the old woman's house, the firemen throw kerosene on the woman's books, but are surprised when she rushes forward and will not leave despite Montag pleading with her. When he leaves, she is the one who strikes the match burning her house, her books, and herself.
This event troubles Montag as he continues to question his job and beliefs. This woman is willing to die with her books. If she is willing to make this great sacrifice, he must question what he and his fellow firemen do and if it's as beneficial to society as he once thought.