Doctor Thomas Stockmann
- A practicing medical doctor, the medical officer of the town baths, and the brother of the mayor, who got him the job at the baths. Stockmann is idealistic and excitable. For much of his life he was destitute and lived in the countryside; now he is happy to be fairly prosperous and living in a bustling town.
Mrs. Katherine Stockmann
- Dr. Stockmann's wife. She is loyal and practical and often encourages her husband to think of his family when he is being rash. Morten Kiil is her adoptive father, or grandfather, depending on translation.
- The daughter of Thomas and Katherine, Petra is as idealistic as her father. She is a hard-working teacher, and she is frustrated that the law requires her to teach things she doesn't believe in.
- Peter is Dr. Stockmann's brother. He is also chairman of the baths committee. He is a cautious but sometimes ruthless politician.
- Hovstad is editor of The People's Herald,
the town's leftist newspaper. Although slightly corrupt, he is at heart a political radical.
- Aslaksen is the newspaper's printer. Because he lets the paper print on credit, he has a degree of editorial control. He is also the chairman of the homeowners association, which represents the town's small business class, the majority of voters. He also has great influence with the Temperance Society, and he is a lover of moderation.
- An assistant at the newspaper, he is a radical, like Hovstad, but he is also ambitious and plans to run for office. He is in some way courting Petra.
- A ship captain who has little interest in local politics, Horster provides the hall for Doctor Stockmann's speech, but he is fired from his ship as a result.
- A rich old man, Kiil owns several of the tanneries that Dr. Stockmann implicates in his water pollution report. He is the adoptive father or grandfather (depending on the translation) of Mrs. Stockmann, and his will assigns a good deal of wealth to her and her children.