Her father was the political philosopher William Godwin and her mother was the philosopher and women's rights advocate Mary Wollstonecraft. Mary's mother died 11 days after giving birth to her.
She was raised by her father, who provided her with a rich informal education, encouraging her to adhere to his own anarchist political theories. When she was four, her father married a neighbour, Mary Jane Clairmont , with whom Mary had a troubled relationship. In , Mary began a romance with one of her father's political followers, Percy Bysshe Shelley, who was already married. Together with her stepsister, Claire Clairmont , she and Percy left for France and travelled through Europe.
Upon their return to England, Mary was pregnant with Percy's child. Over the next two years, she and Percy faced ostracism, constant debt and the death of their prematurely born daughter.
They married in late , after the suicide of Percy Shelley's wife, Harriet. In , the couple and Mary's stepsister famously spent a summer with Lord Byron and John William Polidori near Geneva , Switzerland, where Shelley conceived the idea for her novel Frankenstein. The Shelleys left Britain in for Italy, where their second and third children died before Shelley gave birth to her last and only surviving child, Percy Florence Shelley.
In , her husband drowned when his sailboat sank during a storm near Viareggio. A year later, Shelley returned to England and from then on devoted herself to raising her son and her career as a professional author.
