Hayley Okines passed away last night, aged 17.
The teenager had been battling progeria, a genetic condition that left her with the body of a 104-year-old, since she was a toddler.
Doctors had told Hayley's family that she was unlikely to live past the age of 13 but she defied all the odds.
Hayley, who was from East Sussex, talked openly about her condition.
She appeared on a number of TV documentaries and penned an autobiography documenting what it was like to live with progeria.
Her father Mark said she was being treated for pneumonia and had returned home briefly on the day she died.
The Progeria Research Foundation paid tribute to Hayley on its official
Facebook page: "The entire Progeria family mourns together with many as we say goodbye to Hayley Okines, our smart, beautiful and spirited English rose, who passed away today at age 17."
