Methanimine (CH_2_NH) has been detected in different astronomical sources, both galactic (as in several "hot cores", the circumstellar enevolope IRC+10216, and the L183 pre-stellar core) and extragalactic, and is considered a pre-biotic interstellar molecule. Its ground-state rotational spectrum has been studied in the laboratory up to 172GHz, well below the spectral ranges covered by Herschel/HIFI and the ALMA bands 9 and 10. In this laboratory study, we extend into the submillimetre-wave region the detection of the rotational spectrum of CH_2_NH in its vibrational ground state.