Abstract: Two-dimensional (2D) diamond, an atomically thin carbon-based material, not only inherits the exceptional properties of bulk diamond but is also expected to exhibit unique physical characteristics arising from nanoscale effects. Currently, research on 2D diamond remains in its infancy, being primarily driven by theoretical investigations, while experimental efforts have mainly focused on its controllable synthesis and structural characterization. Owing to pronounced interfacial effects, the direct application of conventional high-pressure synthesis methods to nanoscale systems is considerably limited, making it challenging to achieve a stable transition from sp2 to sp3 hybridization, thereby posing numerous critical scientific challenges for the study of 2D diamond. This review systematically summarizes recent theoretical and experimental advances in the structural features, synthesis strategies, and physicochemical properties of 2D diamond, and provides perspectives on future research directions and scientific opportunities in the field of 2D diamond.