<p>The global move to low carbon and sustainable energy systems is creating a huge demand for advanced materials that can improve energy conversion, storage, and use efficiency with the least impact on the environment. Sustainable nanomaterials have been shown to be good candidates because of their unique physicochemical characteristics, tunable nanostructures, large surface areas, and potential for environmentally friendly manufacturing. This article provides a comprehensive review of nanomaterials used in energy applications and the advances made in engineering design, synthesis, fabrication, and implementation of nanomaterials in next-generation energy technologies. This review discusses renewable nanomaterials derived from biomass from agricultural waste, household waste, and natural polymers as alternatives to produce high-performance carbon-based nanomaterials and explores energy-efficient manufacturing methods of nanomaterials, such as low-temperature deposition, spray coating, solution processes, and printing to allow for large-scale and sustainable manufacturing of devices. In addition to discussing the use of carbon-based nanomaterials, metal oxide nanostructures, and multifunctional nanocomposites in solar energy conversion, electrochemical energy storage, photocatalysis, and emerging renewable energy systems; we will also highlight the of engineering nanostructures, defect modulations, interface designs, and heterostructure formations to increase charge transport, catalytic performance, light harvesting, and electrochemical performance for sustainable nanomaterial technologies. Recent developments show that sustainable nanomaterials can achieve competitive photovoltaic efficiency, large specific capacitance, and high energy storage while limiting reliance on critical raw materials and energy-intensive processing methods. Finally, sustainability metrics, life-cycle analysis, recyclability, circular economy, and commercialization issues are assessed to provide a balanced approach toward future development and deployment of sustainable nanomaterial technologies. This review provides a comprehensive engineering framework that links sustainable nanomaterial design with green manufacturing, device performance, and environmental sustainability. The information presented in this review is expected to assist in the development of large-scale, cost-effective, and environmentally friendly energy technologies for future energy conversion and energy storage systems.</p>