William Halse Rivers Rivers FRS FRAI ((1864-03-12)12 March 1864 – (1922-06-04)4 June 1922) was an English anthropologist, neurologist, ethnologist and psychiatrist known for treatment of First World War officers suffering shell shock, so they could be returned to combat. Rivers' most famous patient was the war poet Siegfried Sassoon, with whom he remained close friends until his own sudden death.

During the early years of the 20th century, Rivers developed new lines of psychological research. He was the first to use a double-blind procedure in investigating physical and psychological effects of consumption of tea, coffee, alcohol, and drugs. For a time he directed centres for psychological studies at two colleges, and he was made a Fellow of St John's College, Cambridge. He also participated in the Torres Strait Islands expedition of 1898 and his consequent seminal work on the subject of kinship.