Although two‐dimensional (2D) carbon materials are widely investigated, a well‐defined 2D carbon nanosheet with an ordered mesostructure has rarely been realized. Monolayer‐ordered mesoporous carbon nanosheets (OMCNS) were prepared through confinement assembly of resol and F127 in the interlayer of montmorillonite (MONT). The nanoscale distance of the interlayer space of MONT only allow the assembly of resol and F127 in the same plane, leading to ordered mesopores perpendicular to carbon nanosheets, and favor the formation of sp2 carbon, resulting in a high degree of graphitization. The mesopores on the carbon nanosheets provide efficient ion diffusion, and the high degree of graphitization provides a fast electron‐transport route, enabling OMCNS as excellent electrode materials for electric double layer capacitors. Ordered mesoporous carbon nanosheets (OMCNS) were prepared through confinement assembly of resol (see picture: blue) and F127 (yellow) in the interlayer of montmorillonite (MONT). The nanoscale interlayer space of MONT only allows the assembly of resol and F127 in the same plane, leading to ordered mesopores perpendicular to carbon nanosheets after carbonization.