The photocatalytic water splitting technique is a promising alternative to produce hydrogen using a facile and proficient method. In the current Review, recent progress made in photocatalytic hydrogen evolution reaction (HER) using 2D nanomaterials (NMs) and composite heterostructures is described. The strong in-plane chemical bonds along with weak van der Waals interaction make these materials lucrative for surface-related applications. State-of-the-art protocols designed for the synthesis of 2D NMs is discussed in detail. The Review illustrates density functional theory (DFT)-based studies against the new set of 2D NMs, which also highlights the importance of structural defects and doping in the electronic structure. Additionally, the Review describes the influence of electronic, structural, and surface manipulation strategies. These impact the electronic structures, intrinsic conductivity, and finally output toward HER. Moreover, this Review also provides a fresh perspective on the prospects and challenges existing behind the application and fabrication strategies.