Charlotte is a pragmatic, 22-year-old woman from a farming family. She travels to Sanditon as a guest of the Parkers, stepping into a society fueled by ambition and hypochondria. Although she considers herself observant and reasonable, her lack of experience leaves her struggling to judge the true nature of the town's elite. She closely watches the local society and learns to spot the vanity and ambition hiding behind polite manners.

Thomas is an energetic, imaginative businessman obsessed with transforming the small coastal village of Sanditon into a profitable health resort. He believes fiercely in the healing powers of saline air and sea bathing. Though friendly and well-meaning, his entrepreneurial ambitions bind him to the whims of his wealthy business partner. He acts as Charlotte's mentor but proves unreliable in his assessment of people due to his financial entanglements.

Lady Denham is the wealthiest resident of Sanditon and the primary investor in the town's resort expansion. Twice widowed, she secured her massive estate through marriage and fiercely guards her fortune from her relatives. She presents a blunt, polite exterior but acts ruthlessly regarding money. She treats those around her as pawns, dictating their lives through financial dependency and demanding performative gratitude.

Diana is Thomas's sister, a talkative woman who claims to suffer from severe health issues. Despite declaring that the sea air will kill her, she bustles with energy and constantly inserts herself into other people's affairs. She uses her self-diagnosed illnesses to make her charity work appear heroic. She is deeply vain, finding a sense of identity and superiority in managing remedies and helping invalids.

Mary is Thomas Parker's wife. She accompanies him on his travels and acts as a gracious host to Charlotte during their stay in Sanditon. She often moderates her husband's intense enthusiasms, noting that his siblings tend to exaggerate their poor health. She provides a quieter, grounding presence compared to her husband's restless ambition.

Mr. Heywood is Charlotte's father, a pragmatic farmer who views beach resorts as a passing fad that harms local economies. He rarely leaves his home but values giving his children opportunities he never had.

Mrs. Heywood is Charlotte's mother. She works hard to manage their rural estate and, like her husband, decides to send Charlotte to Sanditon for a broader life experience.

Clara is Lady Denham's poor cousin who has been taken into Sanditon House to live as a companion. Because she lacks independent wealth, her survival relies entirely on Lady Denham's approval. She strikes Charlotte as the beautiful, impoverished heroine of a novel, trapped by her circumstances but observant of the romantic games played around her.

Edward is Lady Denham's nephew and former heir. He reads too many sentimental novels and imagines himself a dashing, passionate seducer. He speaks in grandiose, poetic language that initially charms Charlotte before she realizes his silliness. He must marry a wealthy heiress to secure his financial future, according to his aunt's strict demands.

Esther is Lady Denham's niece, a young woman made somewhat cold by her proximity to poverty and her aunt's manipulative control. She desperately needs a wealthy husband, as she holds no fortune of her own, and is barred from staying at Sanditon House by her aunt's cruelty.

Susan is Thomas Parker's sister. She is thin from taking excessive medicines and regularly undergoes extreme treatments, such as having teeth pulled or leeches applied for her nerves. She shares her sister Diana's obsession with health and self-importance.

Arthur is the youngest Parker sibling, a tall, well-built young man who claims to be extremely frail. He uses his imagined health issues as an excuse for indolence, preferring to stay indoors and indulge in rich foods like heavily buttered toast and cocoa.

Sidney is Thomas Parker's clever and fashionable brother. Unlike his siblings, he does not invent illnesses for himself and openly mocks Diana and Susan's hypochondria as mere imagination. He is relaxed and engaging, though he rarely leaves time for family vacations.

Mrs. Griffiths is a pleasant woman who runs a girls' boarding school. She brings her charges to Sanditon, overseeing their lodgings and managing the medical prescriptions of her wealthiest ward.

Miss Lambe is a seventeen-year-old heiress of mixed racial heritage from Antigua. Extremely wealthy and chronically ill, she travels with her own personal maid and remains under strict medical supervision. Her wealth makes her a primary target for Lady Denham's marriage schemes.

Mr. Hollis was a wealthy landowner who left Sanditon House and a considerable fortune to his widow, Lady Denham. He suffered from an incurable illness before his death. His portrait sits in a small, unnoticed corner of the house he once owned.

Sir Harry Denham was Lady Denham's second husband. He left her with his title and name, securing her place at the top of the local social hierarchy. His portrait hangs prominently over the mantlepiece in the drawing room at Sanditon House.