The second novel from Mary Shelley, written in 1819/20 but not published in full until 1959. The story deals with common Romantic themes, but also incest and suicide.

Narrating from her deathbed, Mathilda tells the story of her unnamed father's confession of incestuous love for her, followed by his suicide by drowning; her relationship with a gifted young poet called Woodville fails to reverse Matilda's emotional withdrawal or prevent her lonely death. The act of writing this short novel distracted Mary Shelley from her grief after the deaths of her one-year-old daughter Clara at Venice in September 1818 and her three-year-old son William in June 1819 in Rome. These losses plunged Mary Shelley into a depression that distanced her emotionally and sexually from Percy Shelley and left her, as he put it, "on the hearth of pale despair".

The story may be seen as a metaphor for what happens when a woman, ignorant of all consequences, follows her own heart while dependent on her male benefactor.

Mary Shelley sent the finished Mathilda to her father in England, to submit for publication. However, though Godwin admired aspects of the novel, he found the incest theme "disgusting and detestable" and failed to return the manuscript despite his daughter's repeated requests. In the light of Percy Shelley's later death by drowning, Mary Shelley came to regard the novel as ominous; she wrote of herself and Jane Williams "driving (like Mathilda) towards the sea to learn if we were to be for ever doomed to misery". The novel was published for the first time in 1959, edited by Elizabeth Nitchie from dispersed papers. It has become possibly Mary Shelley's best-known work after Frankenstein.