The E-meter, originally the electropsychometer, is an electronic device for displaying the electrodermal activity (EDA) of a human being. It is used for auditing in Scientology and divergent groups. The efficacy and legitimacy of Scientology's use of the E-meter has been subject to extensive litigation and in accordance with a federal court order, the Church of Scientology publishes disclaimers declaring that the E-meter "by itself does nothing", is incapable of improving health, and is used specifically for spiritual purposes.

Such devices have been used as research tools in many human studies, and as one of several components of the Leonarde Keeler's polygraph (lie detector) system, which has been widely criticized as ineffective and pseudoscientific by legal experts and psychologists.