We present a comprehensive review of work on the Er3+-doped tellurite glass microsphere laser. We discuss the optical properties of Er3+-doped tellurite glass, including the emission cross section, the absorption cross section, and the lifetime analysis. Whispering-gallery modes in microspheres and fiber-taper coupling schemes are described, and theoretical analysis is performed for optimization. Finally, lasing characteristics such as the threshold, the lasing wavelength, and the temperature dependence of the microsphere laser are analyzed. Microsphere lasers with different Er2O3 doping concentrations have been fabricated and examined. A state-of-the-art L-band microsphere laser with 124.5-µW maximum output power is demonstrated. These miniature microsphere lasers have great potential and have attracted considerable attention because of their versatility for signal processing, fiber communication, and photon computation, as well as laser stabilization and sensing applications.