A two-step synthetic approach was studied to prepare an unprecedented type of vertically stacked ultrathin 2D single-layered ordered-mesoporous-carbon/2D MoS2 layered heteromaterials with well-defined interfaces. The formed 2D mesoporous-carbon layer is as thin as =1 nm (three carbon atoms thick), and can also be defined as a mesoporous carbon nanosheet (MCN). 2D mesoporous phenolic/amiphiphilic surfactant ultrathin nanosheets were firstly in situ grown by supermolecular self-assembly of monomicelles at the interface of 2D MoS2 nanosheets under hydrothermal treatment. Liquid exfoliated MoS2 nanosheets with a thickness of =1 nm are employed as the initial substrate for growth of the mesoporouscarbon layers. During the chemical exfoliation process, the atomic-level defects of the 2D MoS2 nanosheets are formed. After in situ growth, the ordered-mesoporous-carbon nanosheet/MoS2 heteromaterials retain the ultrathin 2D layered-nanosheet structure in large domains. Ordered mesopore arrays with a pore diameter of =9 nm on the surface of the ultrathin nanosheets are clearly observed by high-resolution scanning electron microscopy (HRSEM). The nanosheets exhibit ultrathin thickness, while they retain their mesoporous structure at such a tiny size. The entire nanosheets are quite uniform in thickness and homogeneous on the surface, indicating that the interfaces between the 2D MoS2 nanosheets and the mesoporous-carbon layers are precisely matched and well-defined. The uniform mesostructures can also be demonstrated by atomic force microscopy (AFM) tomography and phase images of the hetero-nanosheets. These results demonstrate the layered nature of both the initial MoS2 and the obtained MoS2/mesoporous-carbon nanosheets.