A surfactant for water/supercritical carbon dioxide microemulsions that can achieve high water dispersion ability, water/supercritical carbon dioxide microemulsion forming ability under a moderate condition, and high water solubilization rate and that reduces burden on the environment and ecosystem. Provided are a surfactant for stabilizing a water/supercritical carbon dioxide microemulsion including a compound of Formula (I) and a water/supercritical carbon dioxide microemulsion including the surfactant. The compound of Formula (I) has the structure: