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 1909 he succeeded Alix Joffroy as chair of clinical psychiatry and brain disorders at the Hôpital Sainte-Anne.^[1]

In 1909 Ballet was elected president of the Société française d'histoire de la médecine,^[2] and in 1912 became a member of the Académie des sciences.

Ballet is remembered for his 1903 publication of Traité de pathologie mentale, which remained a principal reference book on psychiatry for nearly fifty years in France. 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.^[3][4]

Among his other works were a 1888 publication on inner speech in aphasia, Le Langage Interieur et les Diverses Formes de l'Aphasie,^[5] an 1897 treatise on hypochondria and paranoia titled Psychoses et affections nerveuses,^[6] and an historical biography on philosopher Emanuel Swedenborg ("Swedenborg; histoire d'un visionnaire aux XVIIIe siècle"). With Adrien Proust, he published L'Hygiène du neurasthénique, a book that was later translated into English and published as "The Treatment of Neurasthenia".^[7]

• "Ballet's sign": Palsy affecting one or more extraocular muscles, commonly associated with Graves' ophthalmopathy.^[8]

• A Clinical Lesson at the Salpêtrière