Renfield's Syndrome, also called clinical vampirism, is a rare psychiatric disorder in which the sufferer feels a compulsion to consume blood. The disorder, identified by clinical psychologist Richard Noll in 1992, does not appear in the current Diagnostic and Statistical Manual of Mental Disorders (DSM-IV). According to current psychiatric terminology, Renfield's Syndrome is classified as schizophrenia or paraphilia.

Renfield's Syndrome is named after the character Renfield in Bram Stoker's 1987 novel Dracula. Renfield is a mental patient who consumes flies in the belief that he will absorb their life force. Eventually, he begins feeding flies to spiders and spiders to birds, then consuming the birds, to obtain a greater concentration of life force. People who suffer from Renfield's Syndrome commonly believe that they obtain some sort of power or strength through the consumption of blood.

Sufferers of Renfield's Syndrome are overwhelmingly male. The disorder is typically sparked by an event in childhood in which the sufferer associates the sight or taste of blood with excitement. During puberty, the feelings of attraction to blood become sexual in nature.

Renfield's Syndrome typically follows three stages. In the first, autovampirism or autohemophagia, the sufferer drinks his own blood, often cutting himself in order to do so. The second stage is zoophagia, which consists of eating live animals or drinking their blood. Obtaining animal blood from a butcher or slaughterhouse for consumption also falls into this stage.

In the third stage, true vampirism, the sufferer's attention is turned to other human beings. He may steal blood from hospitals or blood banks, or drink blood directly from a living person. Some people with Renfield's Syndrome commit violent crimes, including murder, after entering this stage.

Though Renfield's Syndrome is newly named and has not yet been accepted into the DSM, it is not a new disorder. Noll noted apparent references to the disorder in German psychiatrist Richard van Krafft-Ebing's 1886 text Psychopathia Sexualis and speculated that Stoker may have been familiar with Krafft-Ebing's work.