AbstractEnergy is the essential requirement of daily life. Due to the diminution of the energy sources, it is necessary develop devices that can harvest the wasted energy that exists in the ambient environment. To address this, triboelectric nanogenerators (TENGs) have been developed as an innovative paradigm for energy harvesting. They can harvest the various forms of mechanical energy, including vibrations, walking, ocean waves, human motion, rain drops, flowing water, the motion of an automobile, wind, rotational energy, and mechanical triggering. TENGs can combine the contact electrification and electrostatic induction for energy conversion and operate on four fundamental modes for conversion of mechanical energy into electrical energy to power small‐scale electronics including mobile phones and sensors. The electrical outputs obtained from TENGs depend on the friction of materials that are selected from the triboelectric series on the basis of their electronegativity and electropositivity. Here, a comprehensive overview of the fundamentals of nanogenerators, various operating modes of TENGs and the design of devices that include them, and the performance improvement of this recently emerged technology is presented.