Madame Thénardier is one of the novel's chief antagonists. She is Thénardier's wife, and mother to Éponine, Azelma, Gavroche, and two unnamed sons. At the beginning of the novel, she runs an inn with her husband where they regularly swindle their customers out of money. Like her husband, Mme. Thénardier is conniving, greedy, cruel, and immoral. Though she demonstrates a "hint of sentiment," she also possesses "malice to bestow." Like Thénardier, she is a symbol of deception, sometimes even unwittingly. When we first meet her, Fantine mistakes her for a loving, doting mother and therefore entrusts Cosette to her care. Mme. Thénardier shows no empathy for Fantine's visibly distressed and miserable state. Instead, she immediately sees Fantine's desperate plea as an opportunity to exploit her for money, without a second thought for the woman's suffering. She takes Cosette in, pawns her clothing, and deeply abuses the defenseless child. A prominent symbol of injustice and cruelty, she dresses Cosette in rags and feeds her "little better than the dog."

When we meet her later in the novel, Mme. Thénardier remains unchanged and, unwaveringly loyal to her husband, continues to participate in his depraved schemes, and has even thrown out three of their children. Mme. Thénardier is representative of moral depravity, and unlike other characters in the novel, is wholly irredeemable. She can be juxtaposed with characters like Fantine, Cosette, and Gavroche, who remain fundamentally good despite overwhelming hardship. Mme. Thénardier, on the other hand, embraces her own suffering and allows it to shape her, becoming consumed by cruelty and malice. Mme. Thénardier's tendency to exploit the vulnerable, including Cosette and Fantine, also ties into broader themes about society's tendency to victimize the poor and defenseless. Through Mme. Thénardier, Hugo critiques the societal instinct to prey on those who are most at risk.