Oxygen vacancies implantation is an efficient way to adjust the physical and chemical properties of metal oxide nanomaterials to meet the requirements for particular applications. Through reasonable defects design, oxygen-deficient metal oxides with excellent optical and electrical properties are widely applied for environmental protection and energy uses. This review discusses recent advances in synthetic approaches of oxygen-deficient metal oxides and their applications in photocatalysis, electrocatalysis, and energy storage devices. The perspectives of oxygen-deficient metal oxides for increased energy demand and environmental sustainability are also examined.