Charles Gilbert Chaddock (November 14, 1861 – July 20, 1936) was an American neurologist, psychiatrist, and translator.

He is remembered for describing the Chaddock reflex and is credited with introducing the terms bisexuality, heterosexuality, and homosexuality from German into the English language.

On his return, he again worked at the Asylum, before, in 1892, becoming Professor of Nervous and Mental Diseases at Marion-Sims College, which later became part of the Saint Louis University School of Medicine.

[5] Chaddock introduced his eponymous reflex in 1911, calling it the External Malleolar sign.

[9] Chaddock is credited with the first use of the words heterosexuality and homosexuality in the English language,[1] as well as the first use of the word bisexuality in its sense of being sexually attracted to both women and men,[1][2] in his translation of Richard von Krafft-Ebing's Psychopathia Sexualis in 1892.