<p>With the growing demand for efficient hydrogen evolution reaction (HER) electrocatalysts driven by the global energy transition, composite strategies based on graphene oxide (GO), reduced graphene oxide (rGO), and graphene have attracted significant attention due to their large specific surface area, excellent electrical conductivity, and abundant surface functional groups. This review systematically summarizes the recent progress of GO/rGO/graphene-based composite systems in HER catalysis. First, the multiple synergistic mechanisms by which GO/rGO/graphene enhance HER performance are elucidated from five aspects: construction of conductive networks, dispersion of active components, interfacial electronic coupling, enhancement of mass transfer and structural stability, and defect/functional group-assisted catalysis. Subsequently, typical composite systems are categorized and reviewed, including noble metals, non-noble metals, transition metal compounds, carbon-based and framework-derived materials, heterostructure/interface-engineered systems, and three-dimensional self-supporting electrodes. Combined with comparative electrochemical performance analysis, it is noted that noble metal-based systems exhibit the highest activity, while non-noble metal systems have also achieved significant progress through interface engineering and defect design. Finally, this review directly addresses three critical challenges—unclear dynamic evolution of active sites, lack of quantitative structure–activity relationship models, and insufficient long-term stability—by providing a mechanistic framework (five synergistic mechanisms) and a systematic cross-system performance comparison. These analyses not only identify current research gaps but also provide actionable guidance for future investigations, including in situ characterization, atomic-level precise synthesis, and multi-scale electrode design. Unlike existing reviews that focus solely on single materials or individual functionalities, this review, for the first time, systematically categorizes and compares the HER performance of diverse composite systems from the perspective of five synergistic mechanisms: conductive network formation, dispersion of active components, interfacial electronic coupling, mass transport and stability, and defect/functional group synergy. By establishing a structure–activity relationship framework and presenting a lateral performance comparison table, this review provides a novel systematic reference for the rational design of high-performance GO/rGO/graphene-based HER catalysts.</p>