This Special Issue is devoted to the reports on 2D-based sensors. 2D materials is a fast-developing field of material science. Graphene and other 2D materials, such as transition metal dichalcogenides (TMDs), hexagonal boron nitride (h-BN), and transition metal oxides (TMOs), have attracted significant attention as supporting substrates in a wide variety of biosensing technologies. Due to recent success in the synthesis and engineering of 2D materials, new functionalities became possible by defect engineering, creating heterostructures with various nanomaterials as well as chemical and molecular doping. Although other nanomaterials like carbon nanotubes exhibit as well some degree of tunability, 2D materials due to their planar nature are more compatible with modern fabrication techniques and device integration. Thanks to the thin nature of 2D materials with a large area-to-volume ratio and various reaction sites they are very sensitive to the state of the surface. The 2D material family contains a variety of electronic properties, spanning from metallic/semimetallic (e.g. graphene) to semiconducting (e.g. MoS2, WS2) to insulating (e.g. h-BN). Importantly, through functionalization or defect engineering of 2D materials one can modify the surface chemistry and thus tailor them to selectively respond to certain analytes with extremely high sensitivity. Furthermore, 2D material-based sensors can be fabricated with miniaturised dimensions and feature flexibility, transparency and mechanical strength. All these unique properties make 2D materials excellent candidates for sensing applications.