A regular hydromagnetic oscillation in a simple toroidal discharge has been found for the first time. The externally applied longitudinal magnetic field and high degree of ionization are essential to generation of the oscillation. The observation by magnetic probes and streak camera shows that a plasma column of them=1 helix rotates in the direction of right‐handed screw to the applied magnetic field. The wavelength of helix and rotational frequency depend on the pressure, ion mass, and applied magnetic field. The phase velocity of the plasma helix coincides with the Alfve´n velocity.