  We review the black hole solutions of the ghost-free massive gravity theory
and its bimetric extension and outline the main results on the stability of
these solutions against small perturbations. Massive (bi)-gravity accommodates
exact black hole solutions, analogous to those of General Relativity. In
addition to these solutions, hairy black holes -- solutions with no
correspondent in General Relativity -- have been found numerically, whose
existence is a natural consequence of the absence of Birkhoff's theorem in
these theories. The existence of extra propagating degrees of freedom, makes
the stability properties of these black holes richer and more complex than
those of General Relativity. In particular, the bi-Schwarzschild black hole
exhibits an unstable spherically symmetric mode, while the bi-Kerr geometry is
also generically unstable, both against the spherical mode and against
superradiant instabilities. If astrophysical black holes are described by these
solutions, the superradiant instability of the Kerr solution imposes stringent
bounds on the graviton mass.
