Polyoxometalates (POMs) are promising precursors for constructing electrocatalysts due to their tunable structures, compositions, and sizes. This review summarizes recent advances in POM-derived nanostructures for electrocatalytic applications, including hydrogen evolution reaction (HER), carbon dioxide reduction reaction (CO₂RR), and nitrogen reduction reaction (NRR). The design and synthesis strategies of POM-derived electrocatalysts are introduced, focusing on morphology control, phase control, composite modulation, and heterostructure engineering. The structure-activity relationships of POM-derived nanostructures are discussed for HER, CO₂RR, and NRR applications. Current challenges and future directions of POM-derived nanostructures are also summarized to provide insights for developing high-efficiency electrocatalysts for energy conversion technologies. The excessive use of nonrenewable fossil fuels has led to environmental and climate issues. Green power, which emits little carbon dioxide, is an important energy source. Electrochemical water splitting driven by renewable electricity is considered a green method for hydrogen production. However, the low activity of nickel-based materials in alkaline water electrolysis and the high cost of platinum in proton exchange membrane water electrolysis limit their application. Ammonia is an important energy carrier and raw material. The Haber-Bosch method is still the main method for ammonia production, but it requires high temperature and pressure, consuming a large amount of energy. Electrochemical NRR has shown good efficiency and selectivity, but the design of high-performance nanostructures remains a challenge. CO₂ concentration has exceeded the safety limit, and electrochemical reduction of CO₂ into value-added chemicals is a promising solution. The high bond energy of CO₂ molecules and the regulation of electron consumption and C-C coupling are important for controlling the selectivity of CO₂RR. For both NRR and CO₂RR, HER is inevitably competing due to similar equilibrium potentials. Therefore, the design and preparation of low-cost and high-performance electrocatalysts are key to implementing green power transformation strategies. POMs, with well-defined compositions and configurations, are attractive precursors for nanostructured electrocatalysts if hydrolysis or pyrolysis reactions are well controlled. POMs have been widely reported as platforms or precursors for constructing different types of electrocatalysts for energy conversion applications. This review systematically summarizes the recent advances in POM-derived nanostructures for electrocatalysis applications.Polyoxometalates (POMs) are promising precursors for constructing electrocatalysts due to their tunable structures, compositions, and sizes. This review summarizes recent advances in POM-derived nanostructures for electrocatalytic applications, including hydrogen evolution reaction (HER), carbon dioxide reduction reaction (CO₂RR), and nitrogen reduction reaction (NRR). The design and synthesis strategies of POM-derived electrocatalysts are introduced, focusing on morphology control, phase control, composite modulation, and heterostructure engineering. The structure-activity relationships of POM-derived nanostructures are discussed for HER, CO₂RR, and NRR applications. Current challenges and future directions of POM-derived nanostructures are also summarized to provide insights for developing high-efficiency electrocatalysts for energy conversion technologies. The excessive use of nonrenewable fossil fuels has led to environmental and climate issues. Green power, which emits little carbon dioxide, is an important energy source. Electrochemical water splitting driven by renewable electricity is considered a green method for hydrogen production. However, the low activity of nickel-based materials in alkaline water electrolysis and the high cost of platinum in proton exchange membrane water electrolysis limit their application. Ammonia is an important energy carrier and raw material. The Haber-Bosch method is still the main method for ammonia production, but it requires high temperature and pressure, consuming a large amount of energy. Electrochemical NRR has shown good efficiency and selectivity, but the design of high-performance nanostructures remains a challenge. CO₂ concentration has exceeded the safety limit, and electrochemical reduction of CO₂ into value-added chemicals is a promising solution. The high bond energy of CO₂ molecules and the regulation of electron consumption and C-C coupling are important for controlling the selectivity of CO₂RR. For both NRR and CO₂RR, HER is inevitably competing due to similar equilibrium potentials. Therefore, the design and preparation of low-cost and high-performance electrocatalysts are key to implementing green power transformation strategies. POMs, with well-defined compositions and configurations, are attractive precursors for nanostructured electrocatalysts if hydrolysis or pyrolysis reactions are well controlled. POMs have been widely reported as platforms or precursors for constructing different types of electrocatalysts for energy conversion applications. This review systematically summarizes the recent advances in POM-derived nanostructures for electrocatalysis applications.