A 26-year-old physical chemist from a prominent Jewish family in London. She is dedicated completely to the methodical practice of science and firmly rejects the traditional domestic roles expected by her parents. Her commitment to objective truth and empirical evidence isolates her in male-dominated academic environments, but she thrives when given the autonomy to conduct rigorous research.

The assistant director of the Biophysics Research Unit at King's College. He views the DNA project as his property and deeply resents Rosalind's assignment as lead researcher. Driven by institutional posturing, he continuously attempts to undermine her authority while maintaining the exclusionary, all-male culture of his workplace.

An ambitious American researcher at the Cavendish Laboratory competing to map the structure of DNA. He favors speed and speculative model-building over painstaking data collection, openly disparaging Rosalind's insistence on empirical proof.

A researcher at the Cavendish Laboratory engaged in the race to solve the DNA structure. He relies heavily on theoretical models rather than generating experimental data, often using the diminutive nickname "Rosy" to casually diminish Rosalind's professional standing.

The charismatic head of the Parisian laboratory who fosters an egalitarian environment for his researchers. He quickly recognizes Rosalind's talent, serving as her mentor in X-ray crystallography while blurring the lines between professional and personal interest.

A doctoral student at King's College assigned to assist Rosalind with X-ray crystallography. Enthusiastic and lacking ego, he respects Rosalind's expertise and provides a crucial source of loyal support within an abrasive institutional environment.

The head of the Biophysics Research Unit at King's College who recruits Rosalind to study DNA. He prioritizes the prestige of winning the scientific race over effectively managing his staff, leading to a toxic culture born from his failure to clearly establish leadership roles.

A prominent French physicist who trained under Marie Curie and acts as a guiding figure for Rosalind. Having successfully balanced a scientific career with a family, she serves as a role model who understands the unique obstacles women face in academia.

A genial X-ray crystallographer who fled Mussolini's Italy and now works in Paris. He quickly befriends Rosalind, becoming a trusted confidant who regularly advises her on her research and complex workplace politics.

A scientist at Birkbeck College who bonds with Rosalind over their shared Jewish heritage. He acts as a theoretical counterpart to her experimental work, forming a highly productive and mutually respectful partnership.

An American biophysicist who comes to London to assist with Rosalind's work on viruses. He brings vital expertise to the group and harbors a deep admiration for Rosalind as both a scientist and a person.

Rosalind's brother, who provides a sympathetic ear during her struggles. Unlike their father, Colin is generally supportive of Rosalind's independence and frequently defends her choices during family disputes.

Rosalind's traditional father, deeply involved in London's post-war Jewish community. He views Rosalind's career as an eccentric pursuit, preferring she focus on philanthropic work, marriage, and faith.

Rosalind's cousin and a steady presence in her personal life. She offers Rosalind a social outlet outside the laboratory and fiercely defends her when learning about the injustices Rosalind faces at work.

The renowned director of a laboratory at Birkbeck College. He fosters an egalitarian, supportive environment for his researchers, allowing Rosalind the autonomy to lead her own team without enduring institutional sexism.

The native French-speaking wife of Vittorio Luzzati. She welcomes Rosalind to their apartment building in Paris, quickly integrating her into their social circle.

Maurice Wilkins's office mate at King's College. He participates in the adversarial environment against Rosalind but hesitates when Wilkins suggests sharing confidential data with outside competitors.

A member of the Medical Research Council committee and head of the Cavendish unit. He uses his administrative access to view confidential reports, demonstrating a flexible approach to professional ethics.

Colin's wife, who attends family gatherings with the Franklin family. She enjoys Rosalind's cooking and remains a supportive presence when Rosalind vents about her workplace issues.

A newly hired researcher at the Laboratoire Central des Services Chimiques in Paris. She catches Jacques Mering's attention shortly after his prior romantic entanglement concludes.