Tom is a rambunctious, imaginative boy living in St. Petersburg, Missouri. He possesses a vivid imagination and constantly seeks out adventures, often inspired by romanticized tales of pirates and outlaws. He strongly prefers play and mischief over schoolwork or chores, actively resisting the societal expectations placed upon him by the adults in his life.

Becky is the blond-haired, blue-eyed daughter of Judge Thatcher. She is a recent arrival in St. Petersburg and quickly captures Tom's heart. She brings a dramatic flair to their early courtship and easily matches Tom's energy for theatrical responses.

Huckleberry is the son of the town drunkard and lives a life completely free of societal expectations. He sleeps outdoors, wears cast-off clothing, and never attends school or church. The other boys admire his absolute freedom, while the town's mothers cordially dislike his influence.

Injun Joe is a dangerous and vengeful resident of St. Petersburg. He harbors deep, long-standing grudges against several townspeople who he feels have mistreated him in the past. He operates outside the boundaries of polite society and is willing to commit severe crimes to achieve his goals.

Aunt Polly is Tom's guardian and the sister of his late mother. She attempts to enforce discipline and order in Tom's life, though she frequently doubts her own strictness. She is a simple-hearted woman who eagerly tests various pseudoscientific health fads on her household.

Sid is Tom's half-brother who lives with him under Aunt Polly's care. He is quiet and generally well-behaved, functioning as a regular foil to Tom's mischievousness. He genuinely enjoys pointing out Tom's rule-breaking to ensure his brother gets in trouble.

Mary is Tom's older cousin. She is kind and patient, serving as a gentle civilizing force in the household. She assists Tom in preparing for Sunday school and encourages him to present a neat, orderly appearance to the community.

Joe is one of Tom's closest friends and frequent partners in crime. He shares Tom's love for imaginary play, joining him in acting out tales of outlaws and pirates. He often feels similarly oppressed by the strict discipline enforced by his mother.

Muff Potter is a local man known for his heavy drinking. He participates in grave robbing for extra money but lacks the malicious nature of his associate. He is generally harmless and friendly to the local boys, often sharing small items with them.

Doctor Robinson is a medical professional in St. Petersburg who secretly hires local men to steal bodies for anatomical study. His illicit activities place him in direct conflict with dangerous men in the middle of the night.

Judge Thatcher is a prominent, wealthy, and respected citizen in the town. He is Becky's father and an influential figure whom the entire community, including the local children, attempts to impress.

The Widow Douglas is a wealthy, kind-hearted woman living in a prominent house in St. Petersburg. She is generous to the children of the town, particularly Huckleberry Finn, offering them warm hospitality and kindness.

Mr. Dobbins is the local schoolmaster who harbors a secret ambition to become a medical doctor. He keeps an anatomy book in his desk and rules his classroom with strict, often arbitrary physical discipline.

Alfred is a new boy in St. Petersburg whose neat clothing and refined mannerisms provoke Tom into a physical fight. He later serves as a pawn in the romantic drama between Tom and Becky.

Amy is a young girl in the village who was engaged to Tom until he abruptly forgets about her upon seeing Becky. She continues to seek his attention and inadvertently becomes a tool for making Becky jealous.

Mr. Jones, also known as the Welshman, is an older resident who lives near the Widow Douglas. He is courageous and quick to action, taking his sons to investigate the danger threatening his neighbor.

Ben is a local boy who unknowingly falls for Tom's psychological trick. He trades his delicious apple for the false privilege of taking over Tom's tedious chore.

Known as the Model Boy, Willie is intensely disliked by the other boys in town. He consistently displays perfect manners and helpfulness, setting an irritatingly high standard that mothers wish their own sons would follow.

Pap is Huckleberry Finn's abusive father. He is known throughout St. Petersburg for his heavy drinking and is largely absent from his son's daily life, appearing primarily to extort money.

Mrs. Thatcher is the wife of Judge Thatcher and mother to Becky. She is a respected member of the community who worries about her daughter's social circle and safety.

Mrs. Harper is Joe's mother. She runs a strict household but deeply loves her son, mourning him intensely when he runs away to Jackson's Island.

Jim is a local Black boy who works for Aunt Polly. He helps around the house and briefly considers trading his work for a look at Tom's sore toe before being chased back to his duties.

Peter is the household cat under Aunt Polly's roof. He inadvertently demonstrates the extreme potency of a pseudoscientific health remedy when given a spoonful of Painkiller.

Mr. Walters is the superintendent of the local Sunday school. He eagerly attempts to impress prominent visitors and organizes the distribution of religious prizes to the students.