William Halse Rivers Rivers (1864-1922) was an anthropologist and psychiatrist, best known for his work with shell-shocked soldiers during World War I. Rivers' most famous patient was the poet, Siegfried Sassoon. He is also famous for his participation in the Torres Straits expedition of 1898, and his consequent seminal work on the subject of kinship.

Rivers was born in 1864 in Kent, and studied medicine, later developing an interest in psychology. He taught at the University of Cambridge and joined the university's expedition to the Torres Straits in 1898, subsequently carrying out extensive study of kinship in Melanesia. During the war, he worked at Craiglockhart Military Hospital near Edinburgh, where he applied techniques of psychoanalysis to British officers suffering from various forms of neurosis brought on by their war experiences. Sassoon came to him in 1917 after publicly refusing to return to his regiment, but was treated with sympathy and given much leeway until he voluntarily returned to France. For Rivers, there was a considerable dilemma involved in "curing" his patients simply in order that they could be sent back to the Western Front to die.

After the war, Rivers published the results of his experimental treatment of patients at Craiglockhart. He remained particularly friendly with Sassoon, who regarded him as a mentor. They shared Socialist sympathies. Rivers died suddenly in 1922.

The life of W.H.R. Rivers and his encounter with Sassoon was fictionalised by Pat Barker in the Regeneration Trilogy, a series of three books including Regeneration (1991), The Eye of The Door (1993) and The Ghost Road (1995). The trilogy was greeted with considerable acclaim, with The Ghost Road being awarded the Booker Prize in the year of its publication.