As the demand for green hydrogen (H₂) rapidly increases, the development of water electrolysis technology has been receiving great attention. Indeed, recent remarkable advances in catalyst materials increased the feasibility of water electrolysis for a future H₂ economy and technology. In this review, we summarize representative non-precious group metal-based materials for achieving active and stable water electrolysis performances. Our comprehensive range of the state-of-the-art catalysts includes doped carbon catalysts, metal borides, metal carbides, metal oxides, metal phosphides, metal sulfides, and single-atom catalysts. For each class of materials, we focus on the synthesis and catalytic performances of the state-of-the-art materials toward water electrolysis and present the current challenges and outlooks of such materials, along with prospective insights to develop and realize practical systems.