Liquid spreading is of significant interest in science and technology. Although surface topography engineering and liquid surface‐tension regulating can facilitate spreading, the spreading layers in these strategies are inevitably inhomogeneous or contaminated with surfactants. Herein, we show a general strategy to realize the superspreading of liquids on mutually soluble gel surfaces. The cooperation of the hydraulic pressure under liquid phase and liquid‐like property of gel surfaces can dramatically eliminate the local pinning effect and enhance the advancement of three‐phase contact line, thus forming stable and homogeneous superspreading liquid layers. Such liquid layers can be converted into various functional thin polymer films with controlled thicknesses (nm‐ to µm‐scale) through one‐step polymerization of the reactants. Our strategy offers opportunities for large‐scale synthesis of versatile functional thin films for various applications.