A rapid and controllable route is developed for the synthesis of MnO nanoparticles that are encapsulated uniformly in three-dimensional (3D) mesoporous interconnected carbon networks (MnO-MICN) through an efficient microwave-polyol process, combined with a subsequent thermal treatment. The dependence of sodium citrate on the morphology of the Mn-based precursors was investigated systematically. Results show that the unique mesoporous interconnected carbon network (MICN) can not only buffer the large volume expansion of MnO during the electrochemical cycling, but also improve the electrode/electrolyte contact area, favoring the fast Li-ion transport and high specific capacity, superior cyclability, and excellent rate capability. When evaluated as an anode material for lithium-ion batteries, the as-formed 3D MnO-MICN nanocomposite exhibits a highly reversible capacity of 1224 mA h g(-1), with a Coulombic efficiency of ~99% at a current density of 200 mA g(-1) over 200 cycles.