HighlightsA novel strategy was developed to construct ultrathin microfiber composite hydrogel films (< 5 μm) by embedding an electrospun fiber network into a hydrogel.The microfiber composite hydrogel offers tunable modulus in a broad range (from ~ 5 kPa to tens of MPa), which matches the modulus of most biological tissues and organs.The ultrathin configuration and ultrasoft nature allow the microfiber composite hydrogel seamlessly attaching to various rough surfaces.Supplementary InformationThe online version contains supplementary material available at 10.1007/s40820-023-01096-4.