Hazel Grace Lancaster
The main character and narrator of The Fault in Our Stars. Hazel is 16 years old and has been dealing for three years with thyroid cancer that spread to her lungs. She is very close with her mother and father and has largely left behind the friendships she had before she was diagnosed with cancer and pulled from public school. Because she was able to get her GED, Hazel attends classes at a local community college when her health permits. She meets Isaac and Gus at Support Group and becomes romantically involved with Gus until his death.
Augustus "Gus" Waters
Augustus, 16 years old, meets Hazel at a support group for youths with cancer. Augustus lost part of his leg to osteosarcoma years before and is believed to be cancer-free, though he has a relapse midway through the book that leads to his death late in the book. He falls quickly for Hazel and they begin dating, though she is scared of hurting him through her illness. Gus is a witty character who loves metaphor, symbolism, grand romantic gestures, and he wishes to die with dignity for something larger than himself.
Isaac
Isaac is another friend of Hazel and Gus's from Support Group. He lost one eye to cancer before the book began, and loses another early in the book. He and a girl named Monica seem to be passionately in love when the book opens, but she dumps him shortly before he loses his second eye, which leads to great anger and sadness.
Frannie Lancaster, Hazel's mother
Frannie Lancaster obviously loves Hazel very much, but Hazel feels that she is limiting her mother because her mother has had to leave work and devote all of her attention to Hazel and her medical treatments. Late in the book, however, Hazel and the reader learn that, for the past year, Frannie has been pursuing a Masters in Social Work online.
Michael Lancaster, Hazel's father
Michael Lancaster is incredibly emotionally invested in Hazel's survival, though he must continue working to support the family; as a result of this, he appears less in the novel and knows less about Hazel's illness and treatment than other characters. Hazel's father cries often, leading to more guilt on Hazel's part that she is going to leave her family devastated when she dies.
Peter Van Houten
Peter Van Houten is the American author of a fictional novel An Imperial Affliction that exists within The Fault in Our Stars. He is a witty, mean older man and an alcoholic, nothing like Hazel had imagined when reading the book so many times. Van Houten keeps up a correspondence with Gus that leads to Gus and Hazel visiting him in Amsterdam, though the visit is largely unsuccessful. However, Van Houten attends Gus's funeral in America and attempts to apologize to Hazel, whereupon she realizes that he had a young daughter who died of leukemia.
Lidewij Vliegenthart
Lidewij Vliegenthart is Peter Van Houten's secretary and, apparently, his caretaker. She arranges for Gus and Hazel's trip to Amsterdam, leaving Van Houten largely in the dark: she hopes that his meeting fans whom his book has truly touched will distract him from his declining health and habits. She quits this job after the disaster that is the teenagers' visit to his home.
Patrick
Patrick is the leader of the support group that Hazel, Gus, and Isaac attend. He is a survivor of testicular cancer and uses his story and his time to attempt to inspire other young people to continue fighting cancer and communicating about their progress and feelings with one another.
Kaitlyn
Kaitlyn is the only of Hazel's school friends with whom she keeps in touch. Kaitlyn is boy-obsessed and shopping-obsessed, so it is hard for Hazel and Kaitlyn to truly relate to one another; but Kaitlyn keeps conversation with Hazel as light and normal as possible.
Monica
Monica is Isaac's girlfriend until she dumps him, ceasing all communication with him just before his eye operation.
Caroline
Caroline was Augustus's former girlfriend who also died from cancer. Her form of cancer affected her brain, causing her to be very rude and angry as she approached the end of her illness.
Mr. Waters and Mrs. Waters, Augustus's father and mother
Mr. and Mrs. Waters are Augustus's parents, and are very thankful for Hazel's support throughout his illness. They cover their house in religious and uplifting aphorisms.
Dr. Maria
Dr. Maria is one of Hazel's many doctors, one that Hazel especially likes for her honesty and care. She allows Hazel to travel to Amsterdam even though it is a danger to her health, arguing that Hazel's life is still hers to live and enjoy.
