We report a tunable iris using two immiscible liquids. One liquid is opaque and conductive, while the other liquid is clear and insulating. The opaque liquid forms an iris-like opening in its central area on one glass substrate surface. The clear liquid is used to fill the outside space of the opaque liquid. In the voltage-off state, the opening presents the smallest aperture. When a voltage is applied to the liquids, the diameter of the iris is enlarged due to the electrowetting effect. Our results show that the aperture of the iris can be tuned from ~2.3 to ~6.1 mm as the applied voltage is changed from 0 to ~65 V. The response time and the transmittance in the opening area were measured to be ~200 ms and ~85%, respectively. Our adaptive iris has potential applications in beam controls, light shutters, and lab-on-a-chip devices.