Using stretchable nanogenerators to obtain disordered mechanical energy from the environment is an ideal way to realize wearable power supply equipment and self-power electronic devices, and alleviate the energy crisis. It is of great significance to integrate the stretchability into the nanogenerator, which can fit the complex shape of the target object better and is well suitable for wearable electronics. When applied to the human body, it can directly harvest human body mechanical energy to power wearable electronic devices and get rid of the trouble of charging. This paper systematically reviewed nanogenerators in stretchability, focusing on stretchable triboelectric nanogenerators, stretchable piezoelectric nanogenerators, and stretchable hybrid nanogenerators. Their physical mechanism, material selection, structure design, and output performance are discussed in detail. It is concluded that the fabrication methods of various devices can be broadly categorized into the two most important device types, namely fiber-like and planar. A detailed analysis of representative work and the latest progress in the past decade is performed. It is most important that excellent stretchability and high-power output are the key point to realize application value of stretchable nanogenerators. In addition, we discuss opportunities and challenges, as well as future development direction of stretchable nanogenerators.