Gilbert Ballet (March 29, 1853 – March 17, 1916) was a French psychiatrist, neurologist and historian who was a native of Ambazac in the department of Haute-Vienne.
He studied medicine in Limoges and Paris, and subsequently became Chef de clinique under Jean-Martin Charcot (1825–1893) at the Salpêtrière.
In 1900 he became a professor of psychiatry, and in 1904 established the department of psychiatry at Hôtel-Dieu de Paris.
In 1911 Ballet described a disorder he called psychose hallucinatoire chronique, being defined as chronic delirium that consists primarily of hallucinations.
In French psychiatry, "chronic hallucinatory psychosis" was to become classified as a distinct entity, separate from other self-delusional disorders.Among his other works were an 1897 treatise on hypochondria and paranoia titled Psychoses et affections nerveuses, and an historical biography on philosopher Emanuel Swedenborg ("Swedenborg; histoire d'un visionnaire aux XVIIIe siècle").