We demonstrate a liquid iris diaphragm using dielectric force, enabling its aperture to vary from $4\mathrm{mm}$ at the resting state to $1.5\mathrm{mm}$ at $160V_{\mathrm{rms}}$ . The liquid iris is a packaged optical component comprised of transparent oil, opaque ink, and a set of driving electrodes on a glass substrate. The iris aperture shrinks with the dielectric force, which is exerted on the interface between the two nonconductive liquids. The transmittance was measured to exceed 85% with no antireflection coatings over the spectrum of visible light. The maximum electric power consumed is measured to be $5.7\mathrm{mW}$ .