Serious climate changes and energy-related environmentalproblemsare currently critical issues in the world. In order to reduce carbonemissions and save our environment, renewable energy harvesting technologieswill serve as a key solution in the near future. Among them, triboelectricnanogenerators (TENGs), which is one of the most promising mechanicalenergy harvesters by means of contact electrification phenomenon,are explosively developing due to abundant wasting mechanical energysources and a number of superior advantages in a wide availabilityand selection of materials, relatively simple device configurations,and low-cost processing. Significant experimental and theoreticalefforts have been achieved toward understanding fundamental behaviorsand a wide range of demonstrations since its report in 2012. As aresult, considerable technological advancement has been exhibitedand it advances the timeline of achievement in the proposed roadmap.Now, the technology has reached the stage of prototype developmentwith verification of performance beyond the lab scale environmenttoward its commercialization. In this review, distinguished authorsin the world worked together to summarize the state of the art intheory, materials, devices, systems, circuits, and applications inTENG fields. The great research achievements of researchers in thisfield around the world over the past decade are expected to play amajor role in coming to fruition of unexpectedly accelerated technologicaladvances over the next decade.