The global number of megacities is projected to increase from 33 to 43 by 2030. Megacities are critical for the world’s economy; however, their resource management is particularly challenging. The increase of energy demand, in parallel to population growth and climate change, requires urgent investment in sustainable energies. We examine the megacities of Bogotá, Los Angeles, and Jakarta and reveal that the potential geothermal resource base is enough to cover the residential electricity demand by 1.14, 4.25, 1.84 times, respectively. Geothermal energy, a clean baseload resource independent from weather conditions, could significantly contribute to energy needs, improved air quality, and the decarbonization of the world’s megacities. We conclude that it is critical that governments and public are educated about the benefits of geothermal. Moreover, those energy policies coupled with investment in research and development are needed to ensure geothermal is successfully integrated into the future energy mix.