An optical switch based on a deformable liquid droplet is demonstrated. The device consists of a clear liquid droplet surrounded by a black liquid. In the voltage-off state, the incident light is absorbed by the black liquid. As the voltage increases, the dielectric force reshapes the droplet by uplifting its dome. As the dome touches the top substrate, a clear channel is opened, allowing the incident light to pass through. Once the voltage is removed, the deformed droplet relaxes back to its original shape and the channel is closed. Devices based on such an operation mechanism have potential applications in light shutters, variable optical attenuators, adaptive irises, and displays.