Topological quantum dots (TQDs) are 3D topological insulator (TI) nanoparticles, displayingsymmetry-protected surface states with discretized energies. We present a theoretical proposal to harnessthese energy levels in a closed lasing scheme operating in the terahertz (THz) frequency range. In thisscheme, a single TQD lases from its topological surface states in the THz regime when pumped with lowintensity, incoherent THz frequency light. The time scales associated with the system are unusually slow,and we find that lasing occurs with a very low threshold. THz lasers are often bulky or require intricatelyengineered nanostructures. Topological quantum dots present a new, compact and simple platform forTHz lasing. The lasing threshold is so low, we predict that room-temperature blackbody radiation cansubstantially contribute to population inversion, providing a route to room-temperature THz lasing pumpedvia blackbody radiation.