  We report the multiferroic behaviour of MnWO$_4$, a magnetic oxide with
monoclinic crystal structure and spiral long-range magnetic order. Based upon
recent theoretical predictions MnWO$_4$ should exhibit ferroelectric
polarization coexisting with the proper magnetic structure. We have confirmed
the multiferroic state below 13 K by observing a finite electrical polarization
in the magnetically ordered state via pyroelectric current measurements.
