  Rotation of the plane of the polarization of light in the presence of a
magnetic-field, known as the Faraday rotation, is a consequence of the
electromagnetic nature of light and has been utilized in many optical devices.
Current efforts aim to realize the ultrafast Faraday rotation on a
sub-picosecond time scale. Thereby, the Faraday medium should allow an
ultrafast process by which in the presence of an ultrashort intense
magnetic-field, the light polarization rotates. We meet these criteria by
applying an intense single cycle THz magnetic-field to simple molecular liquids
and demonstrate the rotation of the plane of polarization of an optical pulse
traversing the liquids on a sub-picosecond time scale. The effect is attributed
to the deflection of an optically induced instantaneous electric polarization
under the influence the THz magnetic-field. The resolved Faraday rotation
scales linearly with the THz magnetic-field and quadratically with the
molecular polarizability.
