Scout is the narrator and protagonist, a bright, combative, and tomboyish six-year-old at the start of the story. She prefers climbing trees to wearing dresses and is fiercely loyal to her father, Atticus. While intelligent, she struggles to understand the complex social rules and prejudices of her town.

Jem is Scout's older brother and constant companion, aged ten at the beginning of the story. He is brave, curious, and deeply protective of Scout, often acting as a bridge between her childish understanding and the adult world. He is fascinated by the mystery of their reclusive neighbor, Boo Radley.

Atticus is a widowed lawyer and the father of Scout and Jem, known for his immense moral integrity and intelligence. He raises his children with patience, treating them as adults and encouraging independent thought. As the book begins, he is preparing to undertake a controversial legal defense that will affect his family.

Dill is a diminutive, confident, and highly imaginative seven-year-old boy who visits Maycomb every summer. He becomes the third member of the children's trio, bringing with him a fascination for the local mystery of the Radley House. He is a storyteller who often concocts tall tales to hide the painful reality of his unstable family life.

Calpurnia is the Finch family's African American cook and housekeeper who acts as the children's primary maternal figure. She is a stern disciplinarian with a rough hand, but she loves Scout and Jem deeply. She is one of the few literate people in her community and bridges the gap between the white and black worlds of Maycomb.

Boo is a reclusive neighbor who has not been seen outside his house in many years, becoming the subject of terrifying local legends. To the children, he is initially a "malevolent phantom" who stalks the neighborhood at night. Despite his fearsome reputation, his presence is felt through small, mysterious interactions.

Alexandra is Atticus's formidable sister who is obsessed with heredity, social propriety, and family pride. She often clashes with Scout over her tomboyish behavior and believes the Finches are superior to others. She wishes to instill "proper" feminine values in Scout.

Bob Ewell is the despised head of the Ewell family, a clan known for being the poorest and least educated in Maycomb. He is a drunken, aggressive man who lives by the town dump and allows his children to live in squalor. He harbors a deep resentment toward Atticus Finch and the town's black community.

Miss Maudie is a sharp-tongued but kind widow who lives across the street from the Finches and loves gardening. She is a close friend to the children, treating them with respect and serving as a voice of reason against the town's hypocrisy. She is one of Atticus’s strongest supporters in the community.

Tom is a young, hardworking African American field hand known for his kindness and a disabled left arm. He becomes the central figure of the town's tension when he is accused of a serious crime against a white woman.

Heck Tate is the sheriff of Maycomb County who tries to do his job fairly but is often constrained by the prejudices of the town. He respects Atticus deeply and relies on his moral judgment in times of crisis.