Equus is a play by Peter Shaffer written in 1973, telling the story of a psychiatrist who attempts to treat a young man who has a pathological religious/sexual fascination with horses.

Shaffer was inspired to write Equus when he heard of a crime involving a teenage boy who blinded six horses. He set out to construct a fictional account of what might have caused the incident, without knowing any of the details of the crime. The play is essentially a detective story, with the psychiatrist trying to understand the cause of the boy's actions while wrestling with his own sense of purpose.