  We study the hydrodynamic regime of chiral plasmas at high temperature. We
find a new type of gapless collective excitation induced by chiral effects in
an external magnetic field. This is a transverse wave, and it is present even
in incompressible fluids, unlike the chiral magnetic and chiral vortical waves.
The velocity is proportional to the coefficient of the gravitational anomaly.
We briefly discuss the possible relevance of this "chiral Alfv\'en wave" in
physical systems.
