  The shapes of dark halos (e.g. spherical, oblate or triaxial) provide
important clues to the formation history of the halos, to their baryon content
and to the nature of the dark matter. The halo shapes also influence the
dynamics of the galaxy they harbor. This review discusses the current status of
theoretical predictions (halo formation in a cosmological context with and
without a dissipative component) and of the observational constraints on halo
shapes. Halos are neither predicted nor observed to be spherical.
