This paper introduces stretchable, transparent, ionic conductors (STICs) and demonstrates their potential in fabricating advanced devices. STICs combine the properties of ionic conductors, which are solid, stretchable, and transparent, with the high-voltage and high-frequency capabilities of ionic systems. The authors achieve a transparent actuator that can generate an area strain of 167% at 18 kV and a transparent loudspeaker that produces sound across the entire audible range. These devices operate without electrochemical reactions, achieving high transmittance (99.99%) at 550 nm, linear strain beyond 500%, and sheet resistance below 200 Ω/sq. At large stretches and high transmittances, STICs exhibit lower electrical resistance compared to existing stretchable and transparent electronic conductors. The paper also discusses the fundamental limits of electromechanical transduction and the design principles of STICs, highlighting their potential applications in bioelectronics, robotics, and energy harvesting.This paper introduces stretchable, transparent, ionic conductors (STICs) and demonstrates their potential in fabricating advanced devices. STICs combine the properties of ionic conductors, which are solid, stretchable, and transparent, with the high-voltage and high-frequency capabilities of ionic systems. The authors achieve a transparent actuator that can generate an area strain of 167% at 18 kV and a transparent loudspeaker that produces sound across the entire audible range. These devices operate without electrochemical reactions, achieving high transmittance (99.99%) at 550 nm, linear strain beyond 500%, and sheet resistance below 200 Ω/sq. At large stretches and high transmittances, STICs exhibit lower electrical resistance compared to existing stretchable and transparent electronic conductors. The paper also discusses the fundamental limits of electromechanical transduction and the design principles of STICs, highlighting their potential applications in bioelectronics, robotics, and energy harvesting.