Katharine Elizabeth Alan de Mattos (née Stevenson; 1851–1939) was a Scottish author and journalist.
At the age of 30, Katharine moved to London with their two children and, with help from her cousin Robert Louis Stevenson and his friend William Ernest Henley, supported herself by journalism.
The Strange Case of Dr Jekyll and Mr Hyde opens with a dedication to Katharine de Mattos.
In 1888, Fanny Stevenson published a short story, "The Nixie", which Henley recognized as based on Katharine's idea they had discussed the previous year.
[3] This accusation of plagiarism led to a bitter quarrel and rupture of the Stevensons with Henley and de Mattos.