William Wilkie Collins (8 January 1824 – 23 September 1889) was an English novelist and playwright known especially for The Woman in White (1859), a mystery novel and early "sensation novel", and for The Moonstone (1868), which has been proposed as the first modern English detective novel.

Born to the London painter William Collins and his wife, he moved with them to Italy when he was twelve, living there and in France for two years and learning Italian and French. He worked initially as a tea merchant. After Antonina, his first novel, appeared in 1850, Collins met Charles Dickens, who became a friend and mentor. Some of his work appeared in Dickens's journals Household Words and All the Year Round. They also collaborated on drama and fiction. Collins gained financial stability and an international following by the 1860s, but became addicted to the opium he took for his gout, so that his health and writing quality declined in the 1870s and 1880s.

Collins criticised the institution of marriage: he split his time between widow Caroline Graves – living with her for most of his life, treating her daughter as his – and the younger Martha Rudd, by whom he had three children.