Meeting the world’s growing energy needs with minimizing environmental impact has accelerated the use of nanomaterials for harvesting energy. These nanoscale materials known for their enhanced surface activity, tunable electronic features and quantum-level behaviors are enabling compact and efficient systems capable of converting mechanical, thermal, solar, and vibrational energy into electricity. This article presents a focused overview of recent studies using engineered nanomaterials and their composites to capture and convert ambient energy. Materials such as zinc oxide nanowires and polymer-based nanocomposites have shown promise in mechanical energy harvesting. Thermoelectric nanomaterials with optimized grain boundaries and embedded nanoinclusions are effective in converting waste heat into electrical power. Progress in solar energy collection has been driven by quantum dots, perovskite layers, and two-dimensional materials that expand the range and efficiency of light absorption. Triboelectric systems especially those enhanced with carbon nanostructures have demonstrated impressive energy outputs from motion and pressure. The integration of different energy harvesting mechanisms into hybrid systems has opened new pathways for powering wireless sensors, portable electronics, and smart infrastructure. While long-term durability, scalable production, and system integration remain ongoing challenges, advances in material design, nanofabrication techniques, and AI-assisted discovery are steadily addressing these gaps. Nanomaterial-based energy harvesters are becoming a key factor due to their self-powered technologies suited for decentralized and sustainable energy systems.