A coaxial cavity gyrotron with two electron beams includes an electron gun (magnetron injection gun, “MIG,” with two beams), a coaxial beam-wave interaction cavity and an outer magnetic field tube. The coaxial beam-wave interaction cavity consists of two parts: an outer conductor and an inner conductor. The two hollow electron beams produced by the MIG are located between the outer conductor and the inner conductor. The MIG includes inner and outer anodes, with a single cathode located between the anodes. The cathode further includes two emitter rings which produce the two hollow electron beams. The entire gyrotron is immersed in the magnetic field tube such that the magnetic field profile is the same or similar to that for a coaxial gyrotron with one electron beam.