Whilst the theory of General Relativity is easily the force which has successfully passed the largest variety of tests, the late-time acceleration
of the Universe might be the first signs of its breakdown on large distance
scales. As such, theories of massive gravity could play a crucial role.
After reviewing the difficulties in constructing healthy theories of massive
gravity, I will construct an explicit covariant theory of massive gravity
which bypasses most of the usual issues and strongly suggests the existence
of an entirely ghost-free classical theory of massive gravity.