John William Polidori was born in the Soho area of London in 1795. His father was Gaetano Polidori, an Italian writer and scholar who emigrated to London. His mother was an English governess named Anna Maria Pierce.
As a young boy, Polidori went to study at the Catholic Ampleforth College. Later his father sent him to study medicine at the University of Edinburgh. He obtained his degree as a medical doctor at the age of nineteen, after writing his thesis on sleepwalking.
In 1816 Polidori began working as a personal physician for the famous English romantic poet Lord Byron. He accompanied Byron on his travels through Europe, in exile from a messy divorce and multiple accusations of romantic affairs in England. Polidori was present at Geneva's Villa Diodati in the summer of 1816, along with Byron, Percy Shelley, Mary Godwin, and Claire Clairemont. It is during this time that Polidori wrote The Vampyre, based on a story that Byron told during the group's supernatural story contest.
Scholars say that Polidori sent the manuscript of The Vampyre to the Countess of Breuss, who sent the anonymous story to an editor. The New Monthly Magazine published The Vampyre in 1819, attributing the novella to Lord Byron. Both Byron and Polidori disputed the attribution in a protracted literary scandal. Polidori never received payment for the novella.
Polidori's diaries and historical accounts indicate that he and Byron had a tense and difficult relationship. Polidori is said to have accepted payment to keep a journal of his travels with Byron, much to the poet's dismay. Byron dismissed Polidori in 1819. Polidori returned to London in 1820 and died in 1821 at the age of twenty-five. Evidence suggests that he committed suicide by ingesting cyanide after a gambling binge, weighed down by health and financial problems.