Hadley is a quiet, 28-year-old woman from St. Louis who has lived a restricted life following a childhood injury and the deaths of her father, mother, and sister. Seeking a change, she visits a friend in Chicago, where she meets a young, aspiring writer. Hadley desires a life of her own making and finds purpose in supporting her new husband's artistic ambitions, even as the vibrant expatriate world of Paris tests her traditional sensibilities.

Ernest is a 21-year-old war hero and aspiring author who works initially as a journalist. He carries deep psychological scars from his service in Italy during World War I, suffering from severe nightmares and a fear of sleeping in the dark. Driven by an all-consuming ambition to write declarative, true sentences, he relies heavily on Hadley for emotional stability while seeking out new, often chaotic experiences to fuel his fiction.

Pauline is a wealthy and fiercely intelligent editor for Vogue magazine in Paris. She moves comfortably within the glamorous, fast-paced circles of the Right Bank. Confident and thoroughly modern, she represents the shifting social dynamics of the Jazz Age and is established early on as a looming threat to the traditional domestic life Hadley has built.

Kate is Hadley's childhood friend from St. Louis who has relocated to Chicago. She embraces the youthful, energetic atmosphere of the city. Having grown up near Ernest in Oak Park, she possesses firsthand knowledge of his character and actively warns Hadley about his complexities and womanizing tendencies.

Gertrude Stein is an authoritative and highly influential American writer living in Paris. She presides over a prominent literary salon that serves as a central hub for expatriate artists. She takes an immediate interest in Ernest's work, advising him to strip his prose down to direct, declarative sentences.

Ezra is a brilliant, eccentric poet and a central figure in the Parisian expatriate community. He acts as a generous literary mentor, using his extensive connections to help place Ernest's early stories in magazines. He lives a bohemian lifestyle, maintaining an open marriage that introduces Hadley to the radical moral codes of the era.

Chink is a British military officer and a close friend of Ernest from their time serving in World War I. He joins the couple for demanding physical excursions, including a grueling trek across the Great St. Bernard Pass. He provides Ernest with a connection to his past and a safe space to process the lingering trauma of combat.

Don is an American humorist and writer who becomes a steady fixture in the Hemingways' social circle. Unlike the more volatile members of the expatriate community, Don represents honorable and reliable friendship. He admires the couple's bond early on and remains a sympathetic, non-judgmental presence when tensions rise.

Nicknamed "Bumby," John is Hadley and Ernest's only child, born in Toronto before the family returns to Paris. His arrival forces the couple to confront the competing demands of parenthood, financial stability, and artistic freedom.

Harold is a writer and part of the Paris expatriate community. He finds early success when his novel is accepted by a publisher, sparking intense professional jealousy in Ernest. His romantic entanglements during the Fiesta de San Fermin in Pamplona become raw material for Ernest's fiction.

Duff is a charismatic and aristocratic British expatriate known for her heavy drinking and magnetic presence. She commands the attention of the men in her social circle, creating friction and rivalry. Her distinctive mannerisms are closely observed and recorded by Ernest for his writing.

Kitty is a vibrant, modern woman in Paris who quickly befriends Hadley. She represents the contemporary sensibilities of the era, dressing fashionably and engaging actively in the city's gossip. Her friendship provides Hadley with an independent social connection outside of Ernest's direct influence.

Scott is a famous American author who quickly inserts himself into Ernest's life. Brilliant but plagued by insecurity and alcoholism, he vacillates between offering Ernest vital editorial support and causing chaotic public scenes.

Zelda is Scott's glamorous, volatile wife. She views Ernest with deep suspicion and frequently behaves recklessly, such as diving from high rocks in the Mediterranean, embodying the chaotic excess of the Jazz Age.

Sherwood is an established American writer who mentors Ernest early in his career. He provides the couple with letters of introduction and crucial advice to relocate to Paris, setting their entire European journey in motion.

Fonnie is Hadley's pragmatic older sister in St. Louis. She provides Hadley with a place to live after their mother's death but remains highly skeptical of Hadley's romantic correspondence with Ernest, representing the conservative family forces Hadley wishes to escape.

Roland is Fonnie's husband and Hadley's brother-in-law. He lives a conventional life in St. Louis and serves as a background figure in the restricted household Hadley yearns to leave behind.

Grace is Ernest's demanding and exacting mother. She maintains a tense, bitter dynamic with her son, establishing a pattern of familial conflict that Ernest struggles to escape.

Dr. Hemingway is Ernest's father. He lives in the shadow of his forceful wife, Grace, and presides over a tense household that drives Ernest to seek life far from Illinois.

James is Hadley's deceased father, who died by suicide after losing his family's money in the stock market. His tragic end casts a long psychological shadow over Hadley, leaving her fearful of hereditary depression.

Florence is Hadley's deceased mother. Following the family's tragedies, she became overbearing and convinced of Hadley's fragility, keeping her isolated. Hadley spent years caring for Florence during her final illness with Bright's disease.

Alice is Gertrude Stein's partner in Paris. She manages the domestic and social flow of their famous salons, specifically sequestering the wives of artists to allow the men to discuss literature uninterrupted.

Dorothy is Ezra Pound's wife. She confides in Hadley about the emotional complexities of her marriage, revealing the practical difficulties of the bohemian, non-traditional lifestyles embraced by the Parisian expatriates.

Marie is the Hemingways' French housekeeper. She helps manage their daily domestic life in Paris and becomes a supportive, comforting presence for Hadley during Ernest's long absences.

Gerald is a wealthy American expatriate who hosts lavish gatherings on the French Riviera. He curates an immaculate, sun-drenched social world that sharply contrasts with the messy emotional realities of his guests.

Sara is Gerald's wife, a wealthy and sophisticated hostess on the Riviera. She helps cultivate an atmosphere of extreme luxury that draws Ernest away from his simpler life with Hadley.