A THz reverse micromagnetron includes a MEMS-based reverse magnetron configuration in which the anode is located at the center of the magnetron surrounded by a cathode ring. Electrons move radially inward in the combined electric and magnetic cross-fields and can reach orbiting angular frequencies in the THz region, even with a magnetic field of the order of 1 T or less. The THz reverse micromagnetron is portable, operates at room temperature, and can be bright.