Sid: Tom's younger brother. He is well behaved and proper, but lives to get Tom in trouble. Unlike Aunt Polly or Tom's cousin Mary, Sid has a mean streak to go with his upright behavior.
Joe Harper: Joe is Tom's best friend, and has the same taste for trouble and imagination. He runs away to Jackson's Island to be a pirate.
Becky Thatcher: Becky is a spirited, beautiful girl. Tom falls in love with her the first time he sees her. Her strong will challenges Tom throughout their courtship. She and Tom get lost in McDougal's Cave together.
Widow Douglas: The Widow is the richest person in St. Petersburg. She is very kind and loving, and is generous with the town's children. She is very religious, in a sincere way. She takes Huck in as thanks for saving her life.
Huckleberry Finn: Huck is the son of the town drunk and a wild boy. He doesn't go to school, church, or any other social function. He cannot read. He is loved by the children and feared by the adults because he doesn't conform. He is less imaginative or fanciful than Tom, but more practical. He and Tom witness Injun Joe killing Dr. Robinson and eventually find his treasure.
Injun Joe: The villain of the book. He is half-Indian and a hateful, evil criminal who steals and murders without a thought. He murders Dr. Robinson and would have hurt Widow Douglas if Huck hadn't gotten help.
Jim: Aunt Polly's 'colored boy.' Although the book doesn't say, Jim is clearly a servant, most likely a slave. He does most of the work around the house, including a lot of Tom's.
Ben Rogers: Another of Tom's friends in town, although not as good a friend as Joe or Huck. He is the first person Tom tricks into whitewashing the fence.
Jeff Thatcher: Tom's friend and Becky's cousin. Tom tries to get information about Becky from him when she is sick.
Amy Lawrence: Tom's great love before Becky comes to town. He uses her to make Becky jealous.
Mary: Tom's cousin, proper and sweet. She is older and worries about Tom a lot.
Mr. Walters: The Sunday-school teacher, who has a bad opinion of Tom. He is shocked when Tom has enough tickets to get a free Bible.
Judge Thatcher: Becky's father, an important judge. Tom earns his respect by saving Becky's life in the cave.
Willie Mufferson: The 'model boy' of the village. He is very proper and stuck-up and the kind of kid parents tell kids they should act more like. Tom and the rest of the boys in town hate him.
The Schoolmaster: A big, bald man who wears a wig. He is angry that he is just a teacher and wishes he could be something important, like a doctor. He is very mean to the students, but is embarrassed by them on Examination Day.
Dr. Robinson: A young doctor who steals bodies from graves, until he is murdered one night by Injun Joe.
Muff Potter: A lower-class drunk of the town, Potter is a nice man who is framed for Dr. Robinson's murder by Injun Joe.
Mrs. Harper: Joe's mother and a friend of Aunt Polly, she worries about Joe as much as Aunt Polly worries about Tom.
Alfred Temple: Recently moved from St. Louis, Alfred has very nice clothes. Tom beats him up when he first comes to town. Later, Becky flirts with him to make Tom jealous, and Alfred destroys Tom's spelling book.
Unknown Man: Injun Joe's accomplice in his attempted revenge against Widow Douglas. He's not as ruthless as Joe, but is too scared of him to not do what he says.
The Welshman: Mr. Jones, who chases Injun Joe away from the Widow Douglas's house after Huck warns him of the danger.